Advanced polishing pad materials and formulations

ABSTRACT

Embodiments of the present disclosure relate to advanced polishing pads with tunable chemical, material and structural properties, and new methods of manufacturing the same. According to one or more embodiments of the disclosure, it has been discovered that a polishing pad with improved properties may be produced by an additive manufacturing process, such as a three-dimensional (3D) printing process. Embodiments of the present disclosure thus may provide an advanced polishing pad that has discrete features and geometries, formed from at least two different materials that include functional polymers, functional oligomers, reactive diluents, and curing agents. For example, the advanced polishing pad may be formed from a plurality of polymeric layers, by the automated sequential deposition of at least one resin precursor composition followed by at least one curing step, wherein each layer may represent at least one polymer composition, and/or regions of different compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/920,801, filed on Oct. 22, 2015, which is acontinuation-in-part of U.S. patent application Ser. No. 14/887,240,filed on Oct. 19, 2015, which is a continuation-in-part of U.S. patentapplication Ser. No. 14/885,950, filed on Oct. 16, 2015, which are allincorporated herein by reference. The U.S. patent application Ser. No.14/887,240 and U.S. patent application Ser. No. 14/885,950 both claimpriority to U.S. Provisional Patent Application Ser. No. 62/065,193,filed on Oct. 17, 2014 and U.S. Provisional Patent Application Ser. No.62/065,270, filed on Oct. 17, 2014, which are also all incorporatedherein by reference.

BACKGROUND

1. Field

Embodiments disclosed herein generally relate to polishing articles andmethods for manufacturing polishing articles used in polishingprocesses. More specifically, embodiments disclosed herein relate topolishing pads produced by processes that yield improved polishing padproperties and performance, including tunable performance.

2. Description of the Related Art

Chemical mechanical polishing (CMP) is a conventional process that hasbeen used in many different industries to planarize surfaces ofsubstrates. In the semiconductor industry, uniformity of polishing andplanarization has become increasingly important as device feature sizescontinue to decrease. During a CMP process, a substrate, such as asilicon wafer, is mounted on a carrier head with the device surfaceplaced against a rotating polishing pad. The carrier head provides acontrollable load on the substrate to push the device surface againstthe polishing pad. A polishing liquid, such as slurry with abrasiveparticles, is typically supplied to the surface of the moving polishingpad and polishing head. The polishing pad and polishing head applymechanical energy to the substrate, while the pad also helps to controlthe transport of slurry which interacts with the substrate during thepolishing process. Because polishing pads are typically made fromviscoelastic polymeric materials, the mechanical properties of apolishing pad (e.g., elasticity, rebound, hardness, and stiffness), andthe CMP processing conditions have a significant impact on the CMPpolishing performance on both an IC die level (microscopic/nanoscopic)and wafer or global level (macroscopic). For example, CMP process forcesand conditions, such as pad compression, pad rebound, friction, andchanges in temperature during processing, and abrasive aqueous slurrychemistries will impact polishing pad properties and thus CMPperformance.

Chemical mechanical polishing processes performed in a polishing systemwill typically include multiple polishing pads that perform differentparts of the full polishing process. The polishing system typicallyincludes a first polishing pad that is disposed on a first platen, whichproduces a first material removal rate and a first surface finish and afirst flatness on the surface of the substrate. The first polishing stepis typically known as a rough polish step, and is generally performed ata high polishing rate. The system will also typically include at leastone additional polishing pad that is disposed on at least an additionalplaten, which produces a second material removal rate and a secondsurface finish and flatness on the surface of the substrate. The secondpolishing step is typically known as a fine polish step, which isgenerally performed at a slower rate than the rough polishing step. Insome configurations, the system may also include a third polishing padthat is disposed on a third platen, which produces a third removal rateand a third surface finish and flatness on the surface of the substrate.The third polishing step is typically known as a material clearing orbuffing step. The multiple pad polishing process can be used in amulti-step process in which the pads have different polishingcharacteristics and the substrates are subjected to progressively finerpolishing or the polishing characteristics are adjusted to compensatefor different layers that are encountered during polishing, for example,metal lines underlying an oxide surface.

During each of the CMP processing steps, a polishing pad is exposed tocompression and rebound cycles, heating and cooling cycles, and abrasiveslurry chemistries. Eventually the polishing pad becomes worn or“glazed” after polishing a certain number of substrates, and then needsto be replaced or reconditioned.

A conventional polishing pad is typically made by molding, casting orsintering polymeric materials that include polyurethane materials. Inthe case of molding, polishing pads can be made one at a time, e.g., byinjection molding. In the case of casting, the liquid precursor is castand cured into a cake, which is subsequently sliced into individual padpieces. These pad pieces can then be machined to a final thickness. Padsurface features, including grooves which aid in slurry transport, canbe machined into the polishing surface, or be formed as part of theinjection molding process. These methods of manufacturing polishing padsare expensive and time consuming, and often yield non-uniform polishingresults due to the difficulties in the production and control of the padsurface feature dimensions. Non-uniformity has become increasinglyimportant as the dimensions of IC dies and features continue to shrink.

Current pad materials and methods to produce them limit the manipulationand fine control bulk pad properties such as storage modulus (E′) andloss modulus (E″), which play critical roles in pad performance.Therefore, uniform CMP requires a pad material and surface features,such as grooves and channels, with a predictable and finely controlledbalance of storage modulus E′ and loss modulus E″, that are furthermaintained over a CMP processing temperature range, from, for example,about 30° C. to about 90° C. Unfortunately, conventional pad productionvia traditional bulk polymerization and casting and molding techniquesonly provide a modicum of pad property (e.g., modulus) control, becausethe pad is a random mixture of phase separated macromolecular domainsthat are subject to intramolecular repulsive and attractive forces andvariable polymer chain entanglement. For example, the presence of phaseseparated micro and macroscopic structural domains in the bulk pad mayyield an additive combination of non-linear material responses, such asa hysteresis in the storage modulus E′ over multiple heating and coolingcycles that typically occur during the CMP processing of batches ofsubstrates, which may result polishing non-uniformities andunpredictable performance across the batch of substrates.

Because of the drawbacks associated with conventional polishing pads andtheir methods of manufacture, there is a need for new polishing padmaterials and new methods of manufacturing polishing pads that providecontrol of pad feature geometry, and fine control of the pad's material,chemical and physical properties. Such improvements are expected toyield improved polishing uniformity at both a microscopic level andmacroscopic level, such as over the entire substrate.

SUMMARY

Embodiments of the disclosure may provide a polishing pad having apolishing surface that is configured to polish a surface of a substrate,comprising a plurality of first polishing elements that each comprise aplurality of first polymer layers, wherein at least one of the pluralityof first polymer layers forms the polishing surface, and one or moresecond polishing elements that each comprise a plurality of secondpolymer layers, wherein at least a region of each of the one or moresecond polishing elements is disposed between at least one of theplurality of first polishing elements and a supporting surface of thepolishing pad. In some configurations, the plurality of first polymerlayers comprise a first polymer composition and the plurality of secondpolymer layers comprise a second polymer composition. The first polymercomposition may be formed from a first droplet composition and thesecond polymer composition may be formed from a second dropletcomposition. In some embodiments, the second droplet composition maycomprise a greater amount of a resin precursor composition material thanthe first droplet composition, and the resin precursor compositionmaterial may have a glass transition temperature of less than or equalto about 40° C., such as less than or equal to 30° C. In someembodiments, the first droplet comprises a greater amount of oligomersand resin precursor composition materials than the second dropletcomposition, wherein the oligomers and resin precursor compositionmaterials have a functionality greater than or equal to two. In someembodiments, the first droplet composition comprises oligomers and resinprecursor composition materials that have a functionality greater thanor equal to two and the second droplet composition comprises resinprecursor composition materials that have a functionality less than orequal to two.

Embodiments of the disclosure may further provide a polishing pad havinga polishing surface that is configured to polish a surface of asubstrate, comprising a plurality of first polishing elements that eachcomprise a plurality of first polymer layers that comprise a firstpolymer material, wherein at least one of the plurality of first polymerlayers forms the polishing surface, and a base region that is disposedbetween at least one of the plurality of first polishing elements and asupporting surface of the polishing pad, wherein the base regioncomprises a plurality of layers that each comprise a plurality of cureddroplets of a first resin precursor composition material and a pluralityof cured droplets of a second resin precursor composition material.

Embodiments of the disclosure may further provide a method of forming apolishing article, comprising dispensing a first droplet of a firstliquid on a surface of a portion of a polishing body, wherein thesurface comprises a first material formed by curing an amount of thefirst liquid, and exposing the dispensed first droplet of the firstliquid to electromagnetic radiation for a first period of time to onlypartially cure the material within the first droplet, wherein exposingthe dispensed first droplet of the first liquid occurs after a secondperiod of time has elapsed, and the second time starts when the firstdroplet is disposed on the surface. The first droplet may comprises aurethane acrylate, a surface cure photoinitiator and a bulk curephotoinitiator, wherein the bulk cure photoinitiator comprises amaterial selected from a group consisting of benzoin ethers, benzylketals, acetyl phenones, alkyl phenones, and phosphine oxides, and thesurface cure photoinitiator comprises a material selected from a groupconsisting of benzophenone compounds and thioxanthone compounds.

Embodiments of the disclosure may further provide a method of forming apolishing article, comprising dispensing an amount of a first liquid ona surface of a portion of a polishing body, where the surface comprisesa first material formed by curing an amount of the first liquid andexposing the dispensed first amount of the first liquid toelectromagnetic radiation generated from a source for a first period oftime to only partially cure the first amount of the first liquid, andexposing the dispensed first amount of the first liquid occurs after asecond period of time has elapsed. The method may also includedispensing an amount of a second liquid on the surface of the portion ofthe polishing body, wherein the amount of the second liquid ispositioned adjacent to the amount of the first liquid, and exposing thedispensed amount of the second liquid to electromagnetic radiationgenerated from the source for a third period of time to only partiallycure the amount of the second liquid, wherein the amount of first liquidand the amount of second liquid are simultaneously exposed to theelectromagnetic radiation generated from the source.

Embodiments of the disclosure may further provide a method of forming apolishing pad, comprising forming a plurality of layers over a surface,where forming the plurality of layers comprises depositing an amount ofa first composition over one or more regions of a surface, depositing anamount of a second composition over one or more second regions of thesurface, wherein the one or more first regions and the one or moresecond regions form a continuous portion of each of the plurality oflayers, and exposing the one or more first regions and the one or moresecond regions to electromagnetic radiation generated from a source fora first period of time to only partially cure a portion of the dispensedamounts of the first composition and the dispensed amounts of the secondcomposition.

Embodiments of the disclosure may further provide a method of forming apolishing article, comprising forming a plurality of urethane acrylatepolymer layers, wherein forming the plurality of urethane acrylatepolymer layers comprises mixing a first amount of a firstmultifunctional urethane acrylate oligomer, a first amount of a firstmono or multifunctional acrylate monomer and a first amount of a firstcuring agent to form a first precursor formulation that has a firstviscosity that enables the first precursor formulation to be dispensedusing an additive manufacturing process, mixing a second amount of thefirst multifunctional urethane acrylate oligomer, a second amount of thefirst mono or multifunctional acrylate monomer and a second amount ofthe first curing agent to form a second precursor formulation that has asecond viscosity that enables the second precursor formulation to bedispensed using an additive manufacturing process, dispensing the firstprecursor formulation on a first region of a surface by use of theadditive manufacturing process, dispensing the second precursorformulation on a second region of the surface by use of the additivemanufacturing process, and exposing the dispensed first amount of thefirst precursor formulation and the dispensed first amount of the secondprecursor formulation to electromagnetic radiation for a first period oftime to only partially cure the first amount of the first precursorformulation and the first amount of the second precursor formulation.

Embodiments of the disclosure may further provide a method of forming apolishing article, comprising forming a plurality of urethane acrylatepolymer layers, wherein forming the plurality of urethane acrylatepolymer layers comprises dispensing a plurality of droplets of a firstprecursor formulation in a first pattern across a surface of a polishingbody that comprises a first material composition, wherein the firstprecursor formulation comprises a first multifunctional urethaneacrylate oligomer, a first amount of a first multifunctional acrylateprecursor and a first amount of a first curing agent, dispensing aplurality of droplets of a second precursor formulation in a secondpattern across the surface of the polishing body, wherein the secondprecursor formulation comprises the first multifunctional urethaneacrylate oligomer and/or the first multifunctional acrylate precursor,and exposing the dispensed droplets of the first precursor formulationand the dispensed droplets of the second precursor formulation toelectromagnetic radiation for a first period of time to only partiallycure the droplets of the first precursor formulation and the droplets ofthe second precursor formulation.

Embodiments of the disclosure may further provide a polishing pad havinga polishing surface that is configured to polish a surface of asubstrate, comprising a plurality of first polishing elements that eachcomprise a plurality of first polymer layers that comprise a firstpolymer material, wherein at least one of the plurality of first polymerlayers forms the polishing surface, and a base region that is disposedbetween at least one of the plurality of first polishing elements and asupporting surface of the polishing pad. The base region may comprise aplurality of layers that each comprise a plurality of cured droplets ofthe first polymer material and a plurality of cured droplets of a secondpolymer material, and wherein the first polymer material has a firstE′30/E′90 ratio that is greater than 6. In some cases, the secondpolymer material may also have a second E′30/E′90 ratio that is greaterthan 6, and the first E′30/E′90 ratio and the second E′30/E′90 ratio aredifferent.

Embodiments of the disclosure may further provide a polishing pad havinga polishing surface that is configured to polish a surface of asubstrate, comprising a plurality of first polishing elements that eachcomprise a plurality of first polymer layers that comprise a firstpolymer material, wherein at least one of the plurality of first polymerlayers forms the polishing surface, and a base region that is disposedbetween at least one of the plurality of first polishing elements and asupporting surface of the polishing pad, wherein the base regioncomprises a plurality of layers that each comprise a plurality of cureddroplets of the first polymer material and a plurality of cured dropletsof a second polymer material. The first polymer material may have afirst storage modulus and the second polymer material may have a secondstorage modulus, wherein the first storage modulus is greater than thesecond storage modulus, and the base region comprises a greater volumepercent of the second polymer material versus the first polymermaterial.

Embodiments of the disclosure may further provide a polishing pad havinga polishing surface that is configured to polish a surface of asubstrate, comprising a plurality of first polishing elements that aredisposed in a pattern relative to the polishing surface, wherein eachfirst polishing element comprises a plurality of first polymer layersthat comprise a first polymer material, and at least one of theplurality of first polymer layers in each of the first polishingelements forms a portion of the polishing surface, and a base regionthat is disposed between each of the plurality of first polishingelements and a supporting surface of the polishing pad, and the baseregion comprises a second polymer material. The first polymer materialmay have a first E′30/E′90 ratio and the second polymer material mayhave a second E′30/E′90 ratio that is different from the first E′30/E′90ratio.

Embodiments of the disclosure may further provide a polishing pad havinga polishing surface that is configured to polish a surface of asubstrate, comprising a plurality of first polishing elements that aredisposed in a pattern relative to the polishing surface, wherein eachfirst polishing element comprises a plurality of first polymer layersthat comprise a first polymer material, and at least one of theplurality of first polymer layers in each of the first polishingelements forms a portion of the polishing surface, and a base regionthat is disposed between each of the plurality of first polishingelements and a supporting surface of the polishing pad, and the baseregion comprises a second polymer material. The first polymer materialmay have a first tan delta and the second polymer material may have asecond tan delta that is different from the first tan delta. The firstpolymer material in the polishing pad may also include a first E′30/E′90ratio and the second polymer material in the polishing pad may also asecond E′30/E′90 ratio that is different from the first E′30/E′90 ratio,and at least a region of the formed polishing pad has a third E′30/E′90ratio that is different from the first and second E′30/E′90 ratios whenmeasured by loading the region of the polishing pad in a directionnormal to the polishing surface. The region of the polishing pad maygenerally include a subset of the plurality of the first polishingelements (e.g., multiple first polishing elements) and a portion of thebase region that is disposed between each of the first polishingelements in the subset of the first polishing elements and thesupporting surface.

Embodiments of the disclosure may further provide a polishing pad havinga polishing surface that is configured to polish a surface of asubstrate, comprising a plurality of first polishing elements that eachcomprise a plurality of first polymer layers that comprise a firstpolymer material, wherein at least one of the plurality of first polymerlayers forms the polishing surface, and each of the first polymer layersof the first polymer material comprises a plurality of cured droplets ofa first droplet composition, and a base region that is disposed betweeneach of the plurality of first polishing elements and a supportingsurface of the polishing pad, wherein the base region comprises aplurality of layers that each comprise a plurality of cured droplets ofthe first polymer composition and a plurality of cured droplets of asecond droplet composition. The first polymer material in the polishingpad may have a first storage modulus and the second polymer material mayhave a second storage modulus, wherein the first storage modulus isgreater than the second storage modulus, and the base region comprises agreater volume percent of the second polymer material versus the firstpolymer material.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1A is a schematic sectional view of a polishing station.

FIGS. 1B-1E are schematic sectional views of a portion of a polishinghead and polishing pad configuration that are positioned in thepolishing station illustrated in FIG. 1A.

FIGS. 1F-1G is a schematic sectional view of a portion of a polishinghead and polishing pad configuration that are positioned in thepolishing station illustrated in FIG. 1A, according to an embodiment ofthe present disclosure.

FIG. 1H is a schematic sectional view of a portion of a substrate thatis being polished using the polishing station configuration illustratedin FIGS. 1B-1C.

FIG. 1I is a schematic sectional view of a portion of a substrate thatis being polished using the polishing station configuration illustratedin FIGS. 1D-1E.

FIG. 1J is a schematic sectional view of a portion of a substrate thatis being polished using the polishing station configuration illustratedin FIGS. 1F-1G, according to an embodiment of the present disclosure.

FIG. 2A is a schematic isometric and cross-sectional view of a polishingpad according to an embodiment of the present disclosure.

FIG. 2B is a schematic partial top view of a polishing pad according toan embodiment of the present disclosure.

FIG. 2C is a schematic isometric and cross-sectional view of a polishingpad according to an embodiment of the present disclosure.

FIG. 2D is a schematic side cross-sectional view of a portion of apolishing pad according to an embodiment of the present disclosure.

FIG. 2E is a schematic side cross-sectional view of a portion of apolishing pad according to an embodiment of the present disclosure.

FIGS. 2F-2K are top views of polishing pad designs according toembodiments of the present disclosure.

FIG. 3A is a schematic view of a system for manufacturing advancedpolishing pads, according to an embodiment of the present disclosure.

FIG. 3B is a schematic view of a portion of the system illustrated inFIG. 3A, according to an embodiment of the present disclosure.

FIG. 3C is a schematic view of a dispensed droplet disposed on a surfaceof a region of the advanced polishing pad illustrated in FIG. 3B,according to an embodiment of the present disclosure.

FIGS. 4A-4D are top views of pixel charts used to form an advancedpolishing pad, according to at least one embodiment of the presentdisclosure.

FIG. 4E is a schematic top view of a web or roll-to-roll type polishingpad, according to an embodiment of the present disclosure.

FIG. 4F is a schematic side cross-sectional view of a portion of apolishing pad, according to an embodiment of the present disclosure.

FIG. 5A illustrates a plot of tan delta versus temperature for variousmaterials and an advanced polishing pad, according to an embodiment ofthe present disclosure.

FIG. 5B illustrates a plot of stress versus strain for materials thatcan be used in an advanced polishing pad, according to an embodiment ofthe present disclosure.

FIG. 5C illustrates a plot of the change in storage modulus versustemperature for pad materials that are subjected to cyclical processingin polishing system, according to an embodiment of the presentdisclosure.

FIG. 6 is a schematic side cross-sectional view of a portion of apolishing pad according to an embodiment of the present disclosure.

FIG. 7 is a schematic side cross-sectional view of a polishing padhaving a transparent region formed therein, according to an embodimentof the present disclosure.

FIG. 8 is a schematic perspective sectional view of a polishing padincluding a supporting foam layer, according to an embodiment of thepresent disclosure.

FIG. 9A illustrates a plot of tan delta versus temperature for variousmaterials and an advanced polishing pad, according to an embodiment ofthe present disclosure.

FIGS. 9B-9C are each schematic side cross-sectional views of portions ofan advanced polishing pad, according to an embodiment of the presentdisclosure.

To facilitate understanding, common words have been used, wherepossible, to designate identical elements that are common to thefigures. It is contemplated that elements disclosed in one embodimentmay be beneficially utilized on other embodiments without specificrecitation.

DETAILED DESCRIPTION

The present disclosure relates to advanced polishing pads with tunablechemical, material and structural properties, and new methods ofmanufacturing the same. According to one or more embodiments of thedisclosure, it has been discovered that a polishing pad with improvedproperties may be produced by an additive manufacturing process, such asa three-dimensional (3D) printing process. Embodiments of the presentdisclosure provide an advanced polishing pad that has discrete featuresand geometries, formed from at least two different materials that areformed from precursors, or resin precursor compositions, that contain“resin precursor components” that include, but are not restricted tofunctional polymers, functional oligomers, monomers, reactive diluents,flow additives, curing agents, photoinitiators, and cure synergists. Theresin precursor components may also include chemically active materialsand/or compounds such as functional polymers, functional oligomers,monomers, and reactive diluents that may be at least monofunctional, andmay undergo polymerization when exposed to free radicals, Lewis acids,and/or electromagnetic radiation. As one example, an advanced polishingpad may be formed from a plurality of polymeric layers, by the automatedsequential deposition of at least one resin precursor compositionfollowed by at least one curing step, wherein each layer may representat least one polymer composition, and/or regions of differentcompositions. In some embodiments, the layers and/or regions of theadvanced polishing pad may include a composite material structure, suchas a radiation cured polymer that contains at least one filler, such asmetals, semimetal oxides, carbides, nitrides and/or polymer particles.In some embodiments, the fillers may be used to increase abrasionresistance, reduce friction, resist wear, enhance crosslinking and/orthermal conductivity of the entire pad, or certain regions of the pad.Therefore, the advanced polishing pad, including the pad body anddiscrete features produced over, upon, and within the pad body, may beformed simultaneously from a plurality of different materials and/orcompositions of materials, thus enabling micron scale control of the padarchitecture and properties.

Moreover, a polishing pad is provided that includes desirable padpolishing properties over the complete polishing process range. Typicalpolishing pad properties include both static and dynamic properties ofthe polishing pad, which are affected by the individual materials withinthe polishing pad and the composite properties of the complete polishingpad structure. An advanced polishing pad may include regions thatcontain a plurality of discrete materials and/or regions that containgradients in material composition in one or more directions within theformed polishing pad. Examples of some of the mechanical properties thatcan be adjusted to form an advance polishing pad that has desirablepolishing performance over the polishing process range include, but arenot limited to storage modulus E′, loss modulus E″, hardness, yieldstrength, ultimate tensile strength, elongation, thermal conductivity,zeta potential, mass density, surface tension, Poison's ratio, fracturetoughness, surface roughness (R_(a)) and other related properties.Examples of some of the dynamic properties that can be adjusted withinan advanced polishing pad may include, but are not limited to tan delta(tan δ), storage modulus ratio (or E′30/E′90 ratio) and other relatedparameters, such as the energy loss factor (KEL). The energy loss factor(KEL) is related to the elastic rebound and dampening effect of a padmaterial. KEL may be defined by the following equation: KEL=tanδ*10¹²/[E′*(1+(tan δ)²)], where E′ is in Pascals. The KEL is typicallymeasured using the method of Dynamic Mechanical Analysis (DMA) at atemperature of 40° C., and frequency of 1 or 1.6 hertz (Hz). Unlessspecified otherwise, the storage modulus E′, the E′30/E′90 ratio and thepercent recovery measurements provided herein were performed using a DMAtesting process that was performed at a frequency of about 1 hertz (Hz)and a temperature ramp rate of about 5° C./min. By controlling one ormore of the pad properties, an improved the polishing processperformance, improved polishing pad lifetime and improved polishingprocess repeatability can be achieved. Examples of pad configurationsthat exhibit one or more these properties are discussed further below inconjunction with one or more the embodiments discussed herein.

As will be discussed more detail below, storage modulus E′, is animportant factor in assuring that the polishing results are uniformacross a substrate, and thus is a useful metric for polishing padperformance. Storage modulus E′ is typically calculated by dividing anapplied tensile stress by the extensional strain in the elastic linearportion of the stress-strain curve (e.g., slope, or Δy/Δx). Similarly,the ratio of viscous stress to viscous strain is used to define the lossmodulus E″. It is noted that both storage modulus E′ and loss modulus E″are intrinsic material properties, that result from the chemical bondingwithin a material, both intermolecular and intramolecular. Storagemodulus may be measured at a desired temperature using a materialtesting technique, such as dynamic mechanical analysis (DMA) (e.g., ASTMD4065, D4440, and D5279). When comparing properties of differentmaterials it is typical to measure the storage modulus E′ of thematerial at a single temperature, in a range between 25° C. and 40° C.,such as 40° C.

Another relevant metric in polishing pad performance and uniformity isthe measure of the dampening ability of a material, such as thecompression and rebound dampening properties of a polishing pad. Acommon way to measure dampening is to calculate the tan delta (tan δ) ofa material at a desired temperature, where tan δ=loss modulus/storagemodulus=E″/E′. When comparing properties of different materials it istypical to compare the tan δ measurements for materials at a singletemperature, such as 40° C. Unless specified otherwise, the tan δmeasurements provided herein were performed using a DMA testing processthat was performed at a frequency of 1 hertz (Hz) and a temperature ramprate of about 5° C./min. Tan δ is generally a measure of how “viscous”chemical structures in a material respond (e.g., bond rotation, polymerchain slippage and movement) to an applied cyclic strain in comparisonto spring-like elastic chemical structures in the material, such asflexible and coiled aliphatic polymer chains that revert to a preferredlow energy conformation and structure when a force is released. Forexample, the less elastic a material is, when a cyclic load is applied,the response of the viscous molecular segments of the material will lagbehind the elastic molecular segments of the material (phase shift) andheat is generated. The heat generated in a polishing pad duringprocessing of substrates may have an effect on the polishing processresults (e.g., polishing uniformity), and thus should be controlledand/or compensated for by judicious choice of pad materials.

The hardness of the materials in a polishing pad plays a role in thepolishing uniformity results found on a substrate after polishing andthe rate of material removal. Hardness of a material, also oftenmeasured using a Rockwell, Ball or Shore hardness scale, measures amaterials resistance toward indentation and provides an empiricalhardness value, and may track or increase with increasing storagemodulus E′. Pad materials are typically measured using a Shore hardnessscale, which is typically measured using the ASTM D2240 technique.Typically, pad material hardness properties are measured on either aShore A or Shore D scale, which is commonly used for softer or lowstorage modulus E′ polymeric materials, such as polyolefins. Rockwellhardness (e.g., ASTM D785) testing may also be used to test the hardnessof “hard” rigid engineering polymeric materials, such as a thermoplasticand thermoset materials.

Polishing Pad Apparatus and Polishing Methods

FIG. 1A is a schematic sectional view of a polishing station 100 thatmay be positioned within a larger chemical mechanical polishing (CMP)system that contains multiple polishing stations 100. The polishingstation 100 includes a platen 102. The platen 102 may rotate about acentral axis 104. A polishing pad 106 may be placed on the platen 102.Typically, the polishing pad 106 covers an upper surface of the platen102 which is at least one to two times larger than the size of thesubstrate 110 (e.g., substrate diameter) that is to be processed in thepolishing station 100. In one example, the polishing pad 106 and platen102 are between about 6 inches (150 mm) and about 40 inches (1,016 mm)in diameter. The polishing pad 106 includes a polishing surface 112configured to contact and process one or more substrates 110 and asupporting surface 103 that is positioned over a surface of the platen102. The platen 102 supports the polishing pad 106 and rotates thepolishing pad 106 during polishing. A carrier head 108 holds a substrate110 against the polishing surface 112 of the polishing pad 106. Thecarrier head 108 typically includes a flexible diaphragm 111 that isused to urge the substrate 110 against the polishing pad 106 and acarrier ring 109 that is used to correct for an inherently non-uniformpressure distribution found across the substrate's surface during thepolishing process. The carrier head 108 may rotate about a central axis114 and/or move in a sweeping motion to generate relative motionsbetween the substrate 110 and the polishing pad 106.

A delivery arm 118 delivers a polishing fluid 116, such as an abrasiveslurry, is supplied to the polishing surface 112 during polishing. Thepolishing liquid 116 may contain abrasive particles, a pH adjusterand/or chemically active components to enable chemical mechanicalpolishing of the substrate. The slurry chemistry of 116 is designed topolish wafer surfaces and/or features that may include metals, metaloxides, and semimetal oxides. The polishing station 100 also typicallyincludes a pad conditioning assembly 120 that includes a conditioningarm 122 and actuators 124 and 126 that are configured to cause a padconditioning disk 128 (e.g., diamond impregnated disk) to be urgedagainst and sweep across the polishing surface 112 at different timesduring the polishing process cycle to abrade and rejuvenate the surface112 of the polishing pad 106.

FIGS. 1B-1C are schematic sectional views of a portion of the polishinghead 108 and a conventional “hard” or high storage modulus E′ moduluspolishing pad 106A that are positioned in the polishing station 100.FIGS. 1D-1E are schematic sectional views of a portion of the polishinghead 108 and a conventional soft or low storage modulus E′ polishing pad106B that are positioned in the polishing station 100. FIGS. 1F-1G areschematic sectional views of a portion of the polishing head 108 and oneembodiment of an advanced polishing pad 200, which is described furtherbelow, that are positioned in the polishing station 100. For clarity,the flexible diaphragm 111 and upper part of the carrier head 108 havebeen left out of FIGS. 1B-1G. During operation the flexible diaphragm111 (FIG. 1A) is positioned to urge the substrate 110 against thepolishing pad 106A, 106B or an advanced polishing pad 200, and a carrierhead actuator (not shown) that is coupled to a mounting portion (notshown) of the carrier head 108 is configured to separately urge thecarrier head 108 and the retaining ring 109 against the surface of thepolishing pad 106A, 106B or advanced polishing pad 200. As shown inFIGS. 1C, 1E and 1F, the flexible diaphragm 111 is configured to apply apressure to the backside of the substrate 110, which is illustrated bythe applied force F₂, and the carrier head actuator is configured toapply a force F₁ to the retaining ring 109.

FIG. 1B illustrates a portion of an edge of a substrate 110 that ispositioned within the carrier head 108 and over a portion of aconventional “hard” or high storage modulus E′ polishing pad 106A beforethe polishing process is performed on the substrate 110. The substrate110 includes a layer 110A that has one or more device features 110B(FIG. 1H) that are to be removed and/or planarized during the subsequentCMP process. FIG. 1C illustrates the substrate 110 during a polishingprocess using the conventional “hard” polishing pad 106A illustrated inFIG. 1B. It has been found that CMP processes that use “hard” polishingpads tend to have non-uniform planarization results due to edge effectsfound at the edge of substrate 110 that specifically relate to the needto apply a force F₁ to the retaining ring 109 to compensate for a largerinherent polishing non-uniformity found at the edge of the substrate 110during a CMP process. In other words, the high storage modulus E′, rigidor hard nature of the material used to form the “hard” polishing padcauses a pad rebound or ridge 107A to be formed when the force F₁ isapplied by the retaining ring 109 to the “hard” polishing pad 106A. Theformation of the ridge 107A is generally related to the deformation 107Bof the “hard” polishing pad 106A due to the applied force F₁, whichcauses the edge of the substrate 110 to polish faster than the center ofthe substrate 110. The higher polishing rate at the edge of thesubstrate 110 leads to a “global” CMP planarization non-uniformity(e.g., across the substrate non-uniformity).

FIG. 1H is a schematic sectional view of a portion of the substrate 110that is being polished using the conventional “hard” polishing pad 106A.As shown, the substrate 110 includes a plurality of features 110B thatare formed within the layer 110A, and are removed and/or planarizedduring the CMP process. In this example, the high storage modulus E′,rigid and/or hard nature of the material used to form the “hard”polishing pad 106A will not allow it to significantly deform on amicroscopic scale (e.g., 10 nm-1000 nm feature pitch) when the force F₂is applied by the flexible diaphragm 111 to the substrate 110. In thiscase, the “hard” polishing pad 106A will generally deliver an acceptableamount of planarization and planarization efficiency on a microscopicscale, but achieve poor global planarization results for the reasonsdiscussed above.

FIG. 1D illustrates a portion of an edge of a substrate 110 that ispositioned within the carrier head 108 and over a portion of aconventional soft or low storage modulus E′ polishing pad 106B beforethe polishing process is performed on the substrate 110. The substrate110 includes a layer 110A that has one or more device features 1106(FIG. 1I) that are to be removed and planarized during the subsequentCMP process. FIG. 1E illustrates the substrate 110 during a polishingprocess using the conventional soft or low storage modulus E′ polishingpad 106B illustrated in FIG. 1D. It has been found that CMP processesthat use soft or low storage modulus E′ polishing pads tend to havenon-uniform planarization results due to the relative ease that a softor low storage modulus E′ polishing pad deforms under the applied forceF₁ generated by the retaining ring 109 and the applied force F₂generated by the flexible diaphragm 111 during a CMP process. In otherwords, the soft, flexible and low storage modulus E′ nature of thematerial used to form the soft or low storage modulus E′ polishing pad106B allows the effect that the force F₁, supplied by the retaining ring109, to be minimized, which improves the ability of the pad tocompensate for retaining ring downforce 109. This compressive responseof the low elastic modulus material allows for quick recover ofretaining ring compression and a more consistent polishing rate seenbetween the center and edge of a substrate during the polishing process.Therefore, the use of a soft or low storage modulus E′ polishing padwill lead to more global CMP planarization uniformity.

FIG. 1I is a schematic sectional view of a portion of a substrate thatis being polished using the conventional soft or low storage modulus E′polishing pad 106B. In this example, the flexible or soft or low storagemodulus E′ nature of the material used to form the soft or low storagemodulus E′ polishing pad 106B allows the material to deform on amicroscopic scale (e.g., 10 nm-1000 nm feature pitch) when the force F₂is applied by the flexible diaphragm 111 to the substrate 110. As shownin FIG. 1I, the material in the soft or low storage modulus E′ polishingpad 106B is able to deform and subsequently contact and polish regionsof the layer 110A between the device features 1106. The act ofsimultaneously polishing the tops of the features 1106 and portions ofthe regions between the features 1106 will create planarizationnon-uniformities and other planarization problems. In this case, thesoft or low storage modulus E′ polishing pad 106B will generally deliveran acceptable amount of global planarization, but achieve a poorplanarization efficiency and provide poor dishing results. Low storagemodulus containing polishing pads provide the benefit on the microscopicscale of improved scratch performance as they allow hard defects, whichcan be disposed between the pad surface and the surface of thesubstrate, to be compressed and/or received within the pad matrix ratherthan forced against the substrate surface by a higher storage modulusmaterial.

Advanced Polishing Pads

Embodiments of the present disclosure generally provide advancedpolishing pads 200 that can be formed by use of an additivemanufacturing process. The advanced polishing pads have a pad body thattypically includes discrete features or regions that are formed from atleast two different material compositions. FIGS. 1F-1 G are schematicsectional views of a portion of the polishing head 108 and a pad body202 of an advanced polishing pad 200 that are positioned in thepolishing station 100. In general, it is desirable to form an advancedpolishing pad 200 that is configured such that the load applied duringthe polishing process is distributed through regions of the polishingbody 202 that include two or more material compositions to improve theadvanced pad's mechanical, structural, and/or dynamic properties. In oneembodiment, the pad body 202 may include a least a first polishingelement 204 that is formed from a first storage modulus E′ material(e.g., high storage modulus E′ material), and a second polishing element206 that may be formed from a second storage modulus E′ material (e.g.,medium or low storage modulus E′ material). In one configuration, aheight 150 of the first polishing element(s) 204 from the supportingsurface 203 is higher than a height 151 of the second polishingelement(s) 206 so that upper surfaces 208 of the first polishing element204 protrude above the second polishing element(s) 206. In one example,as shown in FIG. 1G, the force F₂ is delivered by the flexible diaphragm111 through the first polishing elements 204 to the second polishingelement 206 that is supported by a supporting member, such as the platen102 shown in FIG. 1A, so as to form an advanced polishing pad that hasdesired mechanical and dynamic properties that are a combination ofmaterials in each of the polishing elements. By separating the higherstorage modulus type polishing features from a low storage modulus typesupporting feature the advanced polishing pad offers the benefit ofimproved global planarity, while maintaining the benefit of improved dieand array level planarity offered by a higher storage modulus top pad.

FIG. 1J is a schematic sectional view of a portion of a substrate 110that is being polished using an advanced polishing pad 200, according toan embodiment of the present disclosure. As illustrated in FIG. 1J, insome embodiments, a first polishing element 204 within the polishingbody 202 is formed such that it is large enough to span the distance ofat least two or more device features 110B (e.g., integrated circuitdevices) that are formed on a surface of the substrate 110. In someembodiments, one or more of the first polishing elements 204 are sizedsuch that they are smaller than the major dimension of the substrate(e.g., radius of a circular substrate), but larger than the smallestdevice feature size found on a substrate 110. In some embodiments, aplurality of the first polishing elements 204 each have a lateraldimension 208L, which is parallel to the polishing surface, that isbetween about 250 micrometers and about 3 mm in size. In one example,where the first polishing elements 204 have a circular, square,rectangular, or triangular cross-section at the polishing surface 208,the lateral dimension (e.g., length 208L) can be the diameter or leg ofthe square, rectangle, or triangle, respectively, of the first polishingelement 204. In another example, where the first polishing elements 204are toroid shaped or arc shaped at the polishing surface 208, thelateral dimension (e.g., width 214) can be the thickness of the toroidor arc when measured along its radius, or even the outer diameter of thetoroid in some cases. The combination of the first polishing elements204 and the one or more second polishing elements 206 can thus be usedto adjust the advanced polishing pad properties and performance toimprove the results of a polishing process performed on a substrateusing the advanced polishing pad, as further discussed below.

In some embodiments, the advanced polishing pad 200 may contain at leastone high storage modulus E′, medium storage modulus E′, and/or lowstorage modulus E′ polishing element, and/or chemical structuralfeature. For example, a high storage modulus E′ material composition maybe at least one, or a mixture of, chemical groups and/or structuralfeatures including aromatic ring(s) and some aliphatic chains. In somecases, the high storage modulus E′ materials have a crosslinking densitygreater than 2%. The high storage modulus E′ compositions may be themost rigid element in an advanced polishing pad and have a high hardnessvalue, and display the least elongation. Medium storage modulus E′compositions may contain a mixture of aromatic rings, crosslinking, butmay contain a greater content of aliphatic chains, ether segments,and/or polyurethane segments, than high storage modulus E′ compositions.The medium storage modulus E′ compositions may have intermediaterigidity, hardness, and display a larger amount of elongation than thehigh storage modulus E′ materials. Low storage modulus E′ compositionsmay contain aliphatic chains, ether segments, and/or polyurethanesegments, with minimal or no contribution from aromatic rings orcrosslinking. The low storage modulus E′ compositions may be flexible,soft, and/or rubber-like.

Materials having desirable low, medium, and/or high storage modulus E′properties at temperatures of 30° C. (E′30) are summarized in Table 1:

TABLE 1 Low Modulus Medium Modulus High Modulus CompositionsCompositions Compositions E′30 5 MPa-100 MPa 100 MPa-500 MPa 500MPa-3000 MPa

In one embodiment, and referring to Table 1, the polishing pad body 202may be formed from at least one viscoelastic materials having differentstorage moduli E′ and/or loss moduli E″. As a result, the pad body mayinclude a first material or a first composition of materials that have afirst storage modulus E′ and loss modulus E″, and a second material or asecond composition of materials that have a second storage modulus E′and loss modulus E″ that is different than the first storage modulus E′and loss modulus E″. In some embodiments, polishing pad surface featuresmay include a plurality of features with one or more form factors ordimensions, and be a mixture of features that have different mechanical,thermal, interfacial and chemical properties. For example, the padsurface features, such as channels, grooves and/or proturbances,disposed over, upon, and within the pad body, may include both higherstorage modulus E′ properties derived from a first material or a firstcomposition of materials and some lower storage modulus E′ propertiesderived from a second material or a second composition of materials thatare more elastic than the first material or the first composition ofmaterials.

The term advanced polishing pad 200 as used herein is intended tobroadly describe an advanced polishing pad that contains one or more ofthe attributes, materials, features and/or properties that are discussedabove and further below. Specific configurations of advanced polishingpads are discussed in conjunction with the examples illustrated in FIGS.2A-2K. Unless otherwise specified, the terms first polishing element(s)204 and the second polishing element(s) 206 are intended to broadlydescribe portions, regions and/or features within the polishing body ofthe advanced polishing pad 200. The specific examples of differentadvanced polishing pad configurations, shown in FIGS. 2A-2K, are notintended to be limiting as to the scope of the disclosure providedherein, since other similar configurations may be formed by use of theone or more of the additive manufacturing processes described herein.

The advanced polishing pads may be formed by a layer by layer automatedsequential deposition of at least one resin precursor compositionfollowed by at least one curing step, wherein each layer may representat least one polymer composition, and/or regions of differentcompositions. The compositions may include functional polymers,functional oligomers, reactive diluents, and curing agents. Thefunctional polymers may include multifunctional acrylate precursorcomponents. To form a plurality of solid polymeric layers, one or morecuring steps may be used, such as exposure of one or more compositionsto UV radiation and/or thermal energy. In this fashion, an entirepolishing pad may be formed from a plurality of polymeric layers by 3Dprinting. A thickness of the cured layer may be from about 0.1 micron toabout 1 mm, such as 5 micron to about 100 microns, and such as 25microns to about 30 microns.

Polishing pads according to the present disclosure may have differingmechanical properties, such as storage modulus E′ and loss modulus E″,across the pad body 202, as reflected by at least one compositionalgradient from polishing element to polishing element. Mechanicalproperties across the polishing pad 200 may be symmetric ornon-symmetric, uniform or non-uniform to achieve target polishing padproperties, which may include static mechanical properties, dynamicmechanical properties and wear properties. The patterns of either of thepolishing elements 204, 206 across the pad body 202 may be radial,concentric, rectangular, spiral, fractal or random according to achievetarget properties including storage modulus E′ and loss modulus E″,across the polishing pad. Advantageously, the 3D printing processenables specific placement of material compositions with desiredproperties in specific pad areas of the pad, or over larger areas of thepad so the properties are combined and represent a greater average ofproperties or a “composite” of the properties.

Advanced Polishing Pad Configuration Examples

FIG. 2A is a schematic perspective sectional view of an advancedpolishing pad 200 a according to one embodiment of the presentdisclosure. One or more first polishing elements 204 a may formed inalternating concentric rings that are coupled to one or more secondpolishing elements 206 a to form a circular pad body 202. In oneembodiment, a height 210 of the first polishing element(s) 204 a fromthe supporting surface 203 is higher than a height 212 of the secondpolishing element(s) 206 a so that the upper surfaces 208 of the firstpolishing element(s) 204 a protrude above the second polishingelement(s) 206 a. In one embodiment, the first polishing element 204 isdisposed over a portion 212A of the second polishing element(s) 206 a.Grooves 218 or channels are formed between the first polishingelement(s) 204 a, and at least include a portion of the second polishingelement(s) 206 a. During polishing, the upper surfaces 208 of the firstpolishing elements 204 a form a polishing surface that contacts thesubstrate, while the grooves 218 retain and channel the polishing fluid.In one embodiment, the first polishing element(s) 204 a are thicker thanthe second polishing element(s) 206 a in a direction normal to a planeparallel to the polishing surface, or upper surface 208, of the pad body202 (i.e., Z-direction in FIG. 2A) so that the channels or grooves 218are formed on the top surface of the pad body 202.

In one embodiment, a width 214 of the first polishing elements 204 a maybe between about 250 microns and about 5 millimeters. The pitch 216between the hard first polishing element(s) 204 a may be between about0.5 millimeters and about 5 millimeters. Each first polishing element204 a may have a width within a range between about 250 microns andabout 2 millimeters. The width 214 and/or the pitch 216 may vary acrossa radius of the advanced polishing pad 200 to define zones of variedhardness.

FIG. 2B is a schematic partial top view of an advanced polishing pad 200b according to an embodiment of the present disclosure. The advancedpolishing pad 200 b is similar to the advanced polishing pad 200 of FIG.2A except that the advanced polishing pad 200 b includes interlockingfirst polishing elements 204 b and second polishing elements 206 b. Thefirst polishing elements 204 b and the second polishing elements 206 bform a plurality of concentric rings. The first polishing elements 204 bmay include protruding vertical ridges 220 and the second polishingelements 206 b may include vertical recesses 222 for receiving thevertical ridges 220. Alternatively, the second polishing elements 206 bmay include protruding ridges while the first polishing elements 204 binclude recesses. By having the second polishing elements 206 binterlock with the first polishing elements 204 b, the advancedpolishing pad 200 b will be mechanically stronger in relation to appliedshear forces, which may be generated during the CMP process and/ormaterial handling. In one embodiment, the first polishing elements andthe second polishing elements may be interlocked to improve the strengthof the polishing pad and improve physical integrity of the polishingpads. The interlocking of the features may be due to physical and/orchemical forces.

FIG. 2C is a schematic perspective sectional view of an advancedpolishing pad 200 c according to an embodiment of the presentdisclosure. The polishing pad 200 c includes a plurality of firstpolishing elements 204 c extending from a base material layer, such asthe second polishing element 206 c. Upper surfaces 208 of the firstpolishing elements 204 c form a polishing surface for contacting thesubstrate during polishing. The first polishing elements 204 c and thesecond polishing elements 206 c have different material and structuralproperties. For example, the first polishing elements 204 c may beformed from a hard material, while the second polishing elements 206 cmay be formed from an soft or low storage modulus E′ material. Thepolishing pad 200 c may be formed by 3D printing, similar to theadvanced polishing pad 200.

The first polishing elements 204 c may be substantially the same size,or may vary in size to create varied mechanical properties, such asvaried storage modulus E′ and/or varied loss modulus E″, across thepolishing pad 200 c. The first polishing elements 204 c may be uniformlydistributed across the polishing pad 200 c, or may be arranged in anon-uniform pattern to achieve target properties in the advancedpolishing pad 200 c.

In FIG. 2C, the first polishing elements 204 c are shown to be circularcolumns extending from the second polishing elements 206 c.Alternatively, the first polishing elements 204 c may be of any suitablecross-sectional shape, for example columns with toroidal, partialtoroidal (e.g., arc), oval, square, rectangular, triangular, polygonal,or other irregular section shapes, or combinations thereof. In oneembodiment, the first polishing elements 204 c may be of differentcross-sectional shapes to tune hardness, mechanical strength or otherdesirable properties of the advanced polishing pad 200 c.

FIG. 2D is a schematic partial side cross-sectional view of a polishingbody 202 of an advanced polishing pad 200 c according to an embodimentof the present disclosure. The advanced polishing pad 200 d is similarto the advanced polishing pad 200 a, 200 b or 200 c of FIGS. 2A-2Cexcept that the advanced polishing pad 200 d includes interlocking firstpolishing elements 204 d and second polishing elements 206 d. The firstpolishing elements 204 d and the second polishing elements 206 d mayinclude a plurality of concentric rings and/or discrete elements thatform part of the pad body 202, which are, for example, illustrated inFIG. 2A, 2B or 2C. In one embodiment, the first polishing elements 204 dmay include protruding sidewalls 224 while the second polishing elements206 d may include regions 225 to receive the protruding sidewalls 224 ofthe first polishing elements 204 d. Alternatively, the second polishingelements 206 d may include protruding sidewalls while the firstpolishing elements 204 d include regions that are configured to receivethe protruding sidewalls. By interlocking the second polishing elements206 c with the first polishing elements 204 d, the advanced polishingpad 200 d may exhibit an increased tensile, compressive and/or shearstrength. Additionally, the interlocking sidewalls prevent the advancedpolishing pad 200 d from being pulled apart.

In one embodiment, the boundaries between the first polishing elements204 d and second polishing elements 206 d include a cohesive transitionfrom at least one composition of material to another, such as atransition or compositional gradient from a first composition used toform the first polishing element 204 d and a second composition used toform the second polishing element 206 d. The cohesiveness of thematerials is a direct result of the additive manufacturing processdescribed herein, which enables micron scale control and intimate mixingof the two or more chemical compositions in a layer by layer additivelyformed structure.

FIG. 2E is a schematic partial sectional view of a polishing padaccording to an embodiment of the present disclosure. The advancedpolishing pad 200 e is similar to the advanced polishing pad 200 d ofFIG. 2D except that the advanced polishing pad 200 e includesdifferently configured interlocking features. The advanced polishing pad200 e may include first polishing elements 204 e and second polishingelements 206 e having a plurality of concentric rings and/or discreteelements. In one embodiment, the first polishing elements 204 e mayinclude horizontal ridges 226 while the second polishing elements 206 emay include horizontal recesses 227 to receive the horizontal ridges 226of the first polishing elements 204 e. Alternatively, the secondpolishing elements 206 e may include horizontal ridges while the firstpolishing elements 204 e include horizontal recesses. In one embodiment,vertical interlocking features, such as the interlocking features ofFIG. 2B and horizontal interlocking features, such as the interlockingfeatures of FIGS. 2D and 2E, may be combined to form an advancedpolishing pad.

FIGS. 2F-2K are schematic plan views of various polishing pad designsaccording to embodiments of the present disclosure. Each of the FIGS.2F-2K include pixel charts having white regions (regions in whitepixels) that represent the first polishing elements 204 f-204 k,respectively, for contacting and polishing a substrate, and blackregions (regions in black pixels) that represent the second polishingelement(s) 206 f-206 k. As similarly discussed herein, the white regionsgenerally protrude over the black regions so that channels are formed inthe black regions between the white regions. In one example, the pixelsin a pixel chart are arranged in a rectangular array type pattern (e.g.,X and Y oriented array) that are used to define the position of thevarious materials within a layer, or a portion of layer, of an advancedpolishing pad. In another example, the pixels in a pixel chart arearranged in a hexagonal close pack array type of pattern (e.g., onepixel surrounded by six nearest neighbors) that are used to define theposition of the various materials within a layer, or a portion of layerof a polishing pad. Polishing slurry may flow through and be retained inthe channels during polishing. The polishing pads shown in FIGS. 2F-2Kmay be formed by depositing a plurality of layers of materials using anadditive manufacturing process. Each of the plurality of layers mayinclude two or more materials to form the first polishing elements 204f-204 k and second polishing element(s) 206 f-206 k. In one embodiment,the first polishing elements 204 f-204 k may be thicker than the secondpolishing element(s) 206 f-206 k in a direction normal to a plane thatis parallel to the plurality of layers of materials so that groovesand/or channels are formed on a top surface of the polishing pad.

FIG. 2F is a schematic pixel chart of an advanced polishing pad design200 f having a plurality of concentric polishing features 204 f. Thepolishing features 204 f may be concentric circles of equal width. Inone embodiment, the second polishing element(s) 206 f may also haveequal width so that the pitch of the first polishing element(s) 204 f isconstant along the radial direction. During polishing, channels betweenthe first polishing element(s) 204 f retain the polishing slurry andprevent rapid loss of the polishing slurry due to a centrifugal forcegenerated by rotation of the polishing pad about its central axis (i.e.,center of concentric circles).

FIG. 2G is a schematic pixel chart of a polishing pad design 200 ghaving a plurality of segmented first polishing elements 204 g arrangedin concentric circles. In one embodiment, the segmented first polishingelements 204 g may have substantially equal length. The segmented firstpolishing elements 204 g may form a plurality of concentric circles. Ineach circle, the segmented first polishing elements 204 g may be equallydistributed within each concentric circle. In one embodiment, thesegmented first polishing elements 204 g may have an equal width in theradial direction. In some embodiments, the segmented first polishingelements 204 g have a substantially equal length irrespective of theradius of the concentric circle (e.g., equal arc length except for thecenter region of the polishing pad). In one embodiment, the secondpolishing element(s) 206 g are disposed between the plurality ofconcentric circles and have an equal width so that the pitch of theconcentric circles is constant. In one embodiment, gaps between thesegmented first polishing elements 204 g may be staggered from circle tocircle to prevent polishing slurry from directly flowing out of thepolishing pad under the centrifugal force generated by rotation of thepolishing pad about its central axis.

FIG. 2H is a schematic pixel chart of a polishing pad design 200 hhaving spiral first polishing elements 204 h disposed over secondpolishing element(s) 206 h. In FIG. 2H, the polishing pad 200 h has fourspiral first polishing elements 204 h extending from a center of thepolishing pad to an edge of the polishing pad. Even though four spiralpolishing features are shown, less or more numbers of spiral firstpolishing elements 204 h may be arranged in similar manner. The spiralfirst polishing elements 204 h define spiral channels 218 h. In oneembodiment, each of the spiral first polishing elements 204 h has aconstant width. In one embodiment, the spiral channels 218 h also have aconstant width. During polishing, the polishing pad may rotate about acentral axis in a direction opposite to the direction of the spiralfirst polishing elements 204 h to retain polishing slurry in the spiralchannels. For example, in FIG. 2H, the spiral first polishing elements204 h and the spiral channels are formed in a counter-clockwisedirection, and thus during polishing the polishing pad may be rotatedclockwise to retain polishing slurry in the spiral channels and on thepolishing pad. In some configurations, each of the spiral channels iscontinuous from the center of the polishing pad to the edge of thepolishing pad. This continuous spiral channels allow polishing slurryalong with any polishing waste to flow from the center of the polishingpad to the edge of the polishing pad. In one embodiment, the polishingpad may be cleaned by rotating the polishing pad in the same directionas the spiral first polishing elements 204 h (e.g., counter-clockwise inFIG. 2H).

FIG. 2I is a schematic pixel chart of a polishing pad design 200 ihaving segmented first polishing elements 204 i arranged in a spiralpattern on second polishing element(s) 206 i. The advanced polishing padillustrated in FIG. 2I is similar to the polishing pad in FIG. 2H exceptthat the first polishing elements 204 i are segmented, and the radialpitch of the first polishing elements 204 i varies. In one embodiment,the radial pitch of the segmented first polishing elements 204 idecreases from a center of the polishing pad to an edge region of thepolishing pad to adjust and/or control the retention of the slurry ondifferent regions of the surface of the polishing pad during processing.

FIG. 2J is a schematic pixel chart of a polishing pad design 200 jhaving a plurality of discrete first polishing elements 204 j formed ina second polishing element(s) 206 j. In one embodiment, each of theplurality of first polishing elements 204 j may be a cylindrical posttype structure, similar to the configuration illustrated in FIG. 2C. Inone embodiment, the plurality of first polishing elements 204 j may havethe same dimension in the plane of the polishing surface. In oneembodiment, the plurality of cylindrical first polishing elements 204 jmay be arranged in concentric circles. In one embodiment, the pluralityof cylindrical first polishing elements 204 j may be arranged in aregular 2D pattern relative to the plane of the polishing surface.

FIG. 2K is a schematic pixel chart of a polishing pad design 200 khaving a plurality of discrete first polishing elements 204 k formedover a second polishing element(s) 206 k. The polishing pad of FIG. 2Kis similar to the polishing pad of FIG. 2J except that some firstpolishing elements 204 k in FIG. 2K may be connected to form one or moreclosed circles. The one or more closed circles may create one or moredams to retain polishing slurry during polishing.

The first polishing elements 204 a-204 k in the designs of FIGS. 2A-2Kmay be formed from an identical material or identical compositions ofmaterials. Alternatively, the material composition and/or materialproperties of the first polishing elements 204 a-204 k in the designs ofFIG. 2A-2K may vary from polishing feature to polishing feature.Individualized material composition and/or material properties allowspolishing pads to be tailored for specific needs.

Additive Manufacturing Apparatus and Process Examples

FIG. 3A is a schematic sectional view of an additive manufacturingsystem 350 that can be used to form an advanced polishing pad using anadditive manufacturing process according to one or more embodiments ofthe present disclosure. An additive manufacturing process may include,but are not limited to a process, such as a polyjet deposition process,inkjet printing process, fused deposition modeling process, binderjetting process, powder bed fusion process, selective laser sinteringprocess, stereolithography process, vat photopolymerization digitallight processing, sheet lamination process, directed energy depositionprocess, or other similar 3D deposition process.

The additive manufacturing system 350 generally includes a precursordelivery section 353, a precursor formulation section 354 and adeposition section 355. The deposition section 355 will generallyinclude an additive manufacturing device, or hereafter printing station300. The advanced polishing pad 200 may be printed on a support 302within the printing station 300. Typically, the advanced polishing pad200 is formed layer by layer using one or more droplet ejecting printers306, such as printer 306A and printer 306B illustrated in FIG. 3A, froma CAD (computer-aided design) program. The printers 306A, 306B and thesupport 302 may move relative to each other during the printing process.

The droplet ejecting printer 306 may include one or more print heads 308having one or more nozzles (e.g. nozzles 309-312) for dispensing liquidprecursors. In the embodiment of FIG. 3A, the droplet ejecting printer306A includes print head 308A that has a nozzle 309 and a print head308B having a nozzle 310. The nozzle 309 may be configured to dispense afirst liquid precursor composition to form a first polymer material,such as a soft or low storage modulus E′ polymer, while the nozzle 310may be used to dispense a second liquid precursor to form a secondpolymer material, such as a hard polymer, or a polymer exhibiting a highstorage modulus E′. The liquid precursor compositions may be dispensedat selected locations or regions to form an advanced polishing pad thathas desirable properties. These selected locations collectively form thetarget printing pattern that can be stored as a CAD-compatible file thatis then read by an electronic controller 305, which controls thedelivery of the droplets from the nozzles of the droplet ejectingprinter 306.

The controller 305 is generally used to facilitate the control andautomation of the components within the additive manufacturing system350, including the printing station 300. The controller 305 can be, forexample, a computer, a programmable logic controller, or an embeddedcontroller. The controller 305 typically includes a central processingunit (CPU) (not shown), memory (not shown), and support circuits forinputs and outputs (I/O) (not shown). The CPU may be one of any form ofcomputer processors that are used in industrial settings for controllingvarious system functions, substrate movement, chamber processes, andcontrol support hardware (e.g., sensors, motors, heaters, etc.), andmonitor the processes performed in the system. The memory is connectedto the CPU, and may be one or more of a readily available non-volatilememory, such as random access memory (RAM), flash memory, read onlymemory (ROM), floppy disk, hard disk, or any other form of digitalstorage, local or remote. Software instructions and data can be codedand stored within the memory for instructing the CPU. The supportcircuits are also connected to the CPU for supporting the processor in aconventional manner. The support circuits may include cache, powersupplies, clock circuits, input/output circuitry, subsystems, and thelike. A program (or computer instructions) readable by the controller305 determines which tasks are performable by the components in theadditive manufacturing system 350. Preferably, the program is softwarereadable by the controller 305 that includes code to perform tasksrelating to monitoring, execution and control of the delivery andpositioning of droplets delivered from the printer 306, and themovement, support, and/or positioning of the components within theprinting station 300 along with the various process tasks and varioussequences being performed in the controller 305.

After 3D printing, the advanced polishing pad 200 may be solidified byuse of a curing device 320 that is disposed within the depositionsection 355 of the additive manufacturing system 350. The curing processperformed by the curing device 320 may be performed by heating theprinted polishing pad to a curing temperature or exposing the pad to oneor more forms of electromagnetic radiation or electron beam curing. Inone example, the curing process may be performed by exposing the printedpolishing pad to radiation 321 generated by an electromagnetic radiationsource, such as a visible light source, an ultraviolet light source, andx-ray source, or other type of electromagnetic wave source that isdisposed within the curing device 320.

The additive manufacturing process offers a convenient and highlycontrollable process for producing advanced polishing pads with discretefeatures formed from different materials and/or different compositionsof materials. In one embodiment, soft or low storage modulus E′ featuresand/or hard or high storage modulus E′ features may be formed using theadditive manufacturing process. For example, the soft or low storagemodulus E′ features of a polishing pad may be formed from the firstcomposition containing polyurethane segments dispensed from the nozzle312 of the printer 306B, and hard or high storage modulus E′ features ofthe polishing pad may be formed from droplets of the second compositiondispensed from the nozzle 310 of the printer 306A.

In another embodiment, the first polishing elements 204 and/or thesecond polishing element(s) 206 may each be formed from a mixture of twoor more compositions. In one example, a first composition may bedispensed in the form of droplets by a first print head, such as theprint head 308A, and the second composition may be dispensed in the formof droplets by a second print head, such as the print head 308B of theprinter 306A. To form first polishing elements 204 with a mixture of thedroplets delivered from multiple print heads requires/includes thealignment of the pixels corresponding to the first polishing elements204 on predetermined pixels within a deposition map found in thecontroller 305. The print head 308A may then align with the pixelscorresponding to where the first polishing elements 204 are to be formedand then dispense droplets on the predetermined pixels. The advancedpolishing pad may thus be formed from a first composition of materialsthat is formed by depositing droplets of a first droplet composition anda second material that comprises a second composition of materials thatis formed by depositing droplets of a second droplet composition.

FIG. 3B is a schematic cross-sectional view of a portion of the printingstation 300 and advanced polishing pad 200 during the pad manufacturingprocess. The printing station 300, as shown in FIG. 3B, includes twoprinters 306A and 306B that are used to sequentially form a portion ofthe advanced polishing pad 200. The portion of the advanced polishingpad 200 shown in FIG. 3B may, for example, include part of either thefirst polishing element 204 or the second polishing elements 206 in thefinally formed advanced polishing pad 200. During processing theprinters 306A and 306B are configured to deliver droplets “A” or “B,”respectively, to a first surface of the support 302 and thensuccessively to a surface of the growing polishing pad that is disposedon the support 302 in a layer by layer process. As shown in FIG. 3B, asecond layer 348 is deposited over a first layer 346 which has beenformed on the support 302. In one embodiment, the second layer 348 isformed over the first layer 346 which has been processed by the curingdevice 320 that is disposed downstream from the printers 306A and 306Bin the pad manufacturing process. In some embodiments, portions of thesecond layer 348 may be simultaneously processed by the curing device320 while one or more of the printers 306A and 306B are depositingdroplets “A” and/or “B” onto the surface 346A of the previously formedlayer 346. In this case, the layer that is currently being formed mayinclude a processed portion 348A and an unprocessed portion 348B thatare disposed on either side of a curing zone 349A. The unprocessedportion 348B generally includes an array of dispensed droplets, such asdispensed droplets 343 and 347, which are deposited on the surface 346Aof the previously formed layer 346 by use of the printers 306B and 306A,respectively.

FIG. 3C is a close up cross-sectional view of a dispensed droplet 343that is disposed on a surface 346A of the previously formed layer 346.Based on the properties of the materials within the dispensed droplet343, and due to surface energy of the surface 346A the dispensed dropletwill spread across the surface an amount that is larger than the size ofthe original dispensed droplet (e.g., droplets “A” or “B”), due tosurface tension. The amount of spread of the dispensed droplet will varyas a function of time from the instant that it is deposited on thesurface 346A. However, after a very short period of time (e.g., <1second) the spread of the droplet will reach an equilibrium size, andhave an equilibrium contact angle α. The spread of the dispensed dropletacross the surface affects the resolution of the placement of thedroplets on the surface of the growing polishing pad, and thus theresolution of the features and material compositions found withinvarious regions of the final polishing pad.

In some embodiments, it is desirable to expose one or both of thedroplets “A” and “B” after they have been contact with the surface ofthe substrate for a period of time to cure, or “fix,” each droplet at adesired size before the droplet has a chance to spread to its uncuredequilibrium size on the surface of the substrate. In this case, theenergy supplied to the dispensed droplet, and surface that it is placedon, by the curing device 320 and the droplet's material composition areadjusted to control the resolution of each of the dispensed droplets.Therefore, one important parameter to control or tune during a 3Dprinting process is the control of the dispensed droplet's surfacetension relative to the surface that it is disposed on. In someembodiments, it is desirable to add one or more curing enhancementcomponents (e.g., photoinitiators) to the droplet's formulation tocontrol the kinetics of the curing process, prevent oxygen inhibition,and/or control the contact angle of the droplet on the surface that itis deposited on. One will note that the curing enhancement componentswill generally include materials that are able to adjust: 1) the amountof bulk curing that occurs in the material in the dispensed dropletduring the initial exposure to a desired amount of electromagneticradiation, 2) the amount of surface curing that occurs in the materialin the dispensed droplet during the initial exposure to a desired amountof electromagnetic radiation, and 3) the amount of surface propertymodification (e.g., additives) to the surface cured region of thedispensed droplet. The amount of surface property modification to thesurface cured region of the dispensed droplet generally includes theadjustment of the surface energy of the cured or partially cured polymerfound at the surface of the dispensed and at least partially cureddroplet.

It has been found that it is desirable to partially cure each dispenseddroplet to “fix” its surface properties and dimensional size during theprinting process. The ability to “fix” the droplet at a desirable sizecan be accomplished by adding a desired amount of at least one curingenhancement components to the droplet's material composition anddelivering a sufficient amount of electromagnetic energy from the curingdevice 320 during the additive manufacturing process. In someembodiments, it is desirable to use a curing device 320 that is able todeliver between about 1 milli-joule per centimeter squared (mJ/cm²) and100 mJ/cm², such as about 10-20 mJ/cm², of ultraviolet (UV) light to thedroplet during the additive layer formation process. The UV radiationmay be provided by any UV source, such as mercury microwave arc lamps(e.g., H bulb, H+ bulb, D bulb, Q bulb, and V bulb type lamps), pulsedxenon flash lamps, high-efficiency UV light emitting diode arrays, andUV lasers. The UV radiation may have a wavelength between about 170 nmand about 500 nm.

In some embodiments, the size of dispensed droplets “A”, “B” may be fromabout 10 to about 200 microns, such as about 50 to about 70 microns.Depending on the surface energy (dynes) of the substrate or polymerlayer that the droplet is dispensed over and upon, the uncured dropletmay spread on and across the surface to a size 343A of between about 10and about 500 microns, such as between about 50 and about 200 microns.In one example, the height of such a droplet may be from about 5 toabout 100 microns, depending on such factors as surface energy, wetting,and/or resin precursor composition which may include other additives,such as flow agents, thickening agents, and surfactants. One source forthe additives is BYK-Gardner GmbH of Geretsried, Germany.

In some embodiments, it is generally desirable to select aphotoinitiator, an amount of the photoinitiator in the dropletcomposition, and the amount of energy supplied by curing device 320 toallow the dispensed droplet to be “fixed” in less than about 1 second,such as less than about 0.5 seconds after the dispensed droplet has comein contact with the surface on which it is to be fixed. The actual timeit takes to partially cure the dispensed droplet, due to the exposure todelivered curing energy, may be longer or shorter than the time that thedroplet resides on the surface before it is exposed to the deliveredradiation, since the curing time of the dispensed droplet will depend onthe amount of radiant energy and wavelength of the energy provide fromthe curing source 320. In one example, an exposure time used topartially cure a 120 micrometer (μm) dispensed droplet is about 0.4microseconds (μs) for a radiant exposure level of about 10-15 mJ/cm² ofUV radiation. In an effort to “fix” the droplet in this short timeframeone must position the dispense nozzle of the droplet ejecting printer306 a short distance from the surface of the surface of the polishingpad, such as between 0.1 and 10 millimeters (mm), or even 0.5 and 1 mm,while the surface 346A of the advanced polishing pad are exposed to theradiation 321 delivered from the curing device 320. It has also beenfound that by controlling droplet composition, the amount of cure of thepreviously formed layer (e.g., surface energy of the previously formedlayer), the amount of energy from the curing device 320 and the amountof the photoinitiator in the droplet composition, the contact angle α ofthe droplet can be controlled to control the fixed droplet size, andthus the resolution of the printing process. In one example, theunderlying layer cure may be a cure of about 70% acrylate conversion. Adroplet that has been fixed, or at least partially cured, is alsoreferred to herein as a cured droplet. In some embodiments, the fixeddroplet size 343A is between about 10 and about 200 microns. In someembodiments, the contact angle, also referred to herein as the dynamiccontact angle (e.g., non-equilibrium contact angle), for a “fixed”droplet can be desirably controlled to a value of at least 50°, such asgreater than 55°, or even greater than 60°, or even greater than 70°.

The resolution of the pixels within a pixel chart that is used to form alayer, or a portion of a layer, by an additive manufacturing process canbe defined by the average “fixed” size of a dispensed droplet. Thematerial composition of a layer, or portion of a layer, can thus bedefined by a “dispensed droplet composition”, which a percentage of thetotal number of pixels within the layer, or portion of the layer, thatinclude droplets of a certain droplet composition. In one example, if aregion of a layer of a formed advanced polishing pad is defined ashaving a dispensed droplet composition of a first dispensed dropletcomposition of 60%, then 60% percent of the pixels within the regionwill include a fixed droplet that includes the first materialcomposition. In cases where a portion of a layer contains more than onematerial composition, it may also be desirable to define the materialcomposition of a region within an advanced polishing pad as having a“material composition ratio.” The material composition ratio is a ratioof the number of pixels that have a first material composition disposedthereon to the number of pixels that have a second material compositiondisposed thereon. In one example, if a region was defined as containing1,000 pixels, which are disposed across an area of a surface, and 600 ofthe pixels contain a fixed droplet of a first droplet composition and400 of the pixels contain a fixed droplet of a second dropletcomposition then the material composition ratio would include a 3:2ratio of the first droplet composition to the second dropletcomposition. In configurations where each pixel may contain greater thanone fixed droplet (e.g., 1.2 droplets per pixel) then the materialcomposition ratio would be defined by the ratio of the number of fixeddroplets of a first material to the number of fixed droplets of a secondmaterial that are found within a defined region. In one example, if aregion was defined as containing 1,000 pixels, and there were 800 fixeddroplet of a first droplet composition and 400 fixed droplets of asecond droplet composition within the region, then the materialcomposition ratio would be 2:1 for this region of the advanced polishingpad.

The amount of curing of the surface of the dispensed droplet that formsthe next underlying layer is an important polishing pad formationprocess parameter, since the amount of curing in this “initial dose”affects the surface energy that the subsequent layer of dispenseddroplets will be exposed to during the additive manufacturing process.The amount of the initial cure dose is also important since it will alsoaffect the amount of curing that each deposited layer will finallyachieve in the formed polishing pad, due to repetitive exposure of eachdeposited layer to additional transmitted curing radiation suppliedthrough the subsequently deposited layers as they are grown thereon. Itis generally desirable to prevent over curing of a formed layer, sinceit will affect the material properties of the over cured materialsand/or the wettability of the surface of the cured layer to subsequentlydeposited dispensed droplets in subsequent steps. In one example, toeffect polymerization of a 10-30 micron thick layer of dispenseddroplets may be performed by dispensing each droplet on a surface andthen exposing the dispensed droplet to UV radiation at a radiantexposure level of between about 10 and about 15 mJ/cm² after a period oftime of between about 0.1 seconds and about 1 second has elapsed.However, in some embodiments, the radiation level delivered during theinitial cure dose may be varied layer by layer. For example, due todiffering dispensed droplet compositions in different layers, the amountof UV radiation exposure in each initial dose may be adjusted to providea desirable level of cure in the currently exposed layer, and also toone or more of the underlying layers.

In some embodiments, it is desirable to control the droplet compositionand the amount of energy delivered from the curing device 320 during theinitial curing step, which is a step in which the deposited layer ofdispensed droplets are directly exposed to the energy provided by thecuring device 320, to cause the layer to only partially cure a desiredamount. In general, it is desirable for the initial curing process topredominantly surface cure the dispensed droplet versus bulk cure thedispensed droplet, since controlling the surface energy of the formedlayer is important for controlling the dispensed droplet size. In oneexample, the amount that a dispensed droplet is partially cured can bedefined by the amount of chemical conversion of the materials in thedispensed droplet. In one example, the conversion of the acrylates foundin a dispensed droplet that is used to form a urethane polyacrylatecontaining layer, is defined by a percentage x, which is calculated bythe equation:

${x = {1 - \frac{\left( {A_{C = C}/A_{C = O}} \right)_{x}}{\left( {A_{C = C}/A_{C = O}} \right)_{0}}}},$

where A_(C=C) and A_(C=O) are the values of the C═C peak at 910 cm⁻¹ andthe C═O peaks at 1700 cm⁻¹ found using FT-IR spectroscopy. Duringpolymerization, C═C bonds within acrylates are converted to C—C bond,while C═O within acrylates has no conversion. The intensity of C═C toC═O hence indicates the acrylate conversion rate. The A_(C=C)/A_(C=O)ratio refers to the relative ratio of C═C to C═O bonds within the cureddroplet, and thus the (A_(C=C)/A_(C=O))₀ denotes the initial ratio ofA_(C=C) to A_(C=O) in the droplet, while (A_(C=C)/A_(C=O))_(x) denotesthe ratio of A_(C=C) to A_(C=O) on the surface of the substrate afterthe droplet has been cured. In some embodiments, the amount that a layeris initially cured may be equal to or greater than about 70% of thedispensed droplet. In some configurations, it may be desirable topartially cure the material in the dispensed droplet during the initialexposure of the dispensed droplet to the curing energy to a level fromabout 70% to about 80%, so that the target contact angle of thedispensed droplet may be attained. It is believed that the uncured orpartially acrylate materials on top surface are copolymerized with thesubsequent droplets, and thus yield cohesion between the layers.

The process of partially curing a dispensed droplet during the initiallayer formation step can also be important to assure that there will besome chemical bonding/adhesion between subsequently deposited layers,due to the presence of residual unbonded groups, such as residualacrylic groups. Since the residual unbonded groups have not beenpolymerized, they can be involved in forming chemical bonds with asubsequently deposited layer. The formation of chemical bonds betweenlayers can thus increase the mechanical strength of the formed advancedpolishing pad in the direction of the layer by layer growth during thepad formation process (e.g., Z-direction in FIG. 3B). As noted above,the bonding between layers may thus be formed by both physical and/orchemical forces.

The mixture of the dispensed droplet, or positioning of the dispenseddroplets, can be adjusted on a layer by layer basis to form layers thatindividually have tunable properties, and a polishing pad that hasdesirable pad properties that are a composite of the formed layers. Inone example, as shown in FIG. 3B, a mixture of dispensed dropletsincludes a 50:50 ratio of the dispensed droplets 343 and 347 (or amaterial composition ratio of 1:1), wherein the dispensed droplet 343includes at least one different material from the material found in thedispensed droplet 347. Properties of portions of the polishing body 202,such as the first polishing elements 204 and/or second polishingelements 206 may be adjusted or tuned according to the ratio and/ordistribution of a first composition and a second composition that areformed from the positioning of the dispensed droplets during thedeposition process. For example, the weight % of the first compositionmay be from about 1% by weight based on total composition weight toabout 100% based on total composition weight. In a similar fashion, thesecond composition may be from about 1% by weight based on totalcomposition weight to about 100% based on total composition weight.Depending on the material properties that are required, such as hardnessand/or storage modulus, compositions of two or more materials can bemixed in different ratios to achieve a desired effect. In oneembodiment, the composition of the first polishing elements 204 and/orsecond polishing elements 206 is controlled by selecting at least onecomposition or a mixture of compositions, and size, location, and/ordensity of the droplets dispensed by one or more printers. Therefore,the controller 305 is generally adapted to position the nozzles 309-310,311-312 to form a layer that has interdigitated droplets that have beenpositioned in a desired density and pattern on the surface of thepolishing pad that is being formed. In some configurations, dispenseddroplets may be deposited in such a way as to ensure that each drop isplaced in a location where it does not blend with other drops, and thuseach remains a discrete material “island” prior to being cured. In someconfigurations, the dispensed droplets may also be placed on top ofprior dispensed droplets within the same layer to increase the buildrate or blend material properties. Placement of droplets relative toeach other on a surface may also be adjusted to allow partial mixingbehavior of each of the dispensed droplets in the layer. In some cases,it may be desirable to place the droplets closer together or fartherapart to provide more or less mixing of the components in theneighboring droplets, respectively. It has been found that controllingdroplet placement relative to other dispensed droplets and thecomposition of each droplet can have an effect on the mechanical andpolishing properties of the formed advanced polishing pad.

Even though only two compositions are generally discussed herein forforming the first polishing elements 204 and/or second polishingelements 206, embodiments of the present disclosure encompass formingfeatures on a polishing pad with a plurality of materials that areinterconnected via compositional gradients. In some configurations, thecomposition of the first polishing elements 204 and/or second polishingelements 206 in a polishing pad are adjusted within a plane parallel tothe polishing surface and/or through the thickness of the polishing pad,as discussed further below.

The ability to form compositional gradients and the ability to tune thechemical content locally, within, and across an advanced polishing padare enabled by “ink jettable” low viscosity compositions, or lowviscosity “inks” in the 3D printing arts that are used to form thedroplets “A” and/or “B” illustrated in FIG. 3B. The low viscosity inksare “pre-polymer” compositions and are the “precursors” to the formedfirst polishing elements 204 and second polishing elements 206 found inthe pad body 202. The low viscosity inks enable the delivery of a widevariety of chemistries and discrete compositions that are not availableby conventional techniques (e.g., molding and casting), and thus enablecontrolled compositional transitions or gradients to be formed withindifferent regions of the pad body 202. This is achieved by the additionand mixing of viscosity thinning reactive diluents to high viscosityfunctional oligomers to achieve the appropriate viscosity formulation,followed by copolymerization of the diluent(s) with the higher viscosityfunctional oligomers when exposed to a curing energy delivered by thecuring device 320. The reactive diluents may also serve as a solvent,thus eliminating the use of inert non-reactive solvents or thinners thatmust be removed at each step.

Referring to the precursor delivery section 353 and precursorformulation section 354 of FIG. 3A, in one embodiment, a first precursor356 is mixed with a second precursor 357 and a diluent 358 to form afirst printable ink composition 359, which is delivered to reservoir304B of the printer 306B, and used to form portions of the polishingbody 202. Similarly, a third precursor 366 can be mixed with a fourthprecursor 367 and a diluent 368 to form a second new printable inkcomposition 369, which is delivered to reservoir 304A of the printer306A, and used to form another portion of the polishing body 202. Insome embodiments, the first precursor 356 and the third precursor 366each comprise an oligomer, such as multifunctional oligomer, the secondprecursor 357 and the fourth precursor 367 each comprise amultifunctional monomer, and diluent 358 and the diluent 368 eachcomprise a reactive diluent (e.g., monomer) and/or initiator (e.g.,photoinitiator). One example of a first printable composition 359 mayinclude a first precursor 356 which includes a reactive difunctionaloligomer, comprising aliphatic chain segments, which may have aviscosity from about 1000 centipoise (cP) at 25° C., to about 12,000 cPat 25° C., is then mixed with and thus diluted by a 10 cP at 25° C.reactive diluent (e.g., diluent 358), such as monoacrylate, to create anew composition that has new viscosity. The printable composition thusobtained may exhibit a viscosity from about 80 cP to about 110 cP at 25°C., and a viscosity from about 15 cP to about 30 cP at 70° C., which maybe effectively dispensed from a 3D printer ink jet nozzle.

FIGS. 4A-4F provide examples of an advanced polishing pads that includea compositional gradient across one or more regions of the polishingbody. In FIGS. 4A-4D, the white pixel marks are intended toschematically illustrate where a dispensed droplet of a first materialis dispensed while the black pixel marks illustrate where no material isdispensed within one or more layers used to form the polishing pad. Byuse of these techniques, compositional gradients in the cured material,or material formed by a plurality of cured droplets, can be formed inthe printed layers used to form at least part of a complete polishingpad. The tailored composition of the printed layers within a polishingpad can be used to adjust and tailor the overall mechanical propertiesof the polishing pad. The composition of polishing features may vary inany suitable pattern. Although polishing pads described herein are shownto be formed from two kinds of materials, this configuration is notintended to be limiting of the scope of the disclosure provided herein,since polishing pads including three or more kinds of materials iswithin the scope of the present disclosure. It should be noted that thecompositions of the polishing features in any designs of the polishingpad, such as the polishing pads in FIGS. 2A-2K, may be varied in similarmanner as the polishing pads in FIGS. 4A-4F.

FIGS. 4A and 4B are black and white bitmap images reflecting pixelcharts of a printed layer within an advanced polishing pad that includesportions of first polishing elements 204 and second polishing element(s)206. In FIGS. 4A and 4B, the white pixel marks are where a droplet of afirst material is dispensed while the black pixel marks are where nomaterial is dispensed and cured. FIG. 4A is the pixel chart 400 a of afirst portion of a layer within an advanced polishing pad 200 and FIG.4B is the pixel chart 400 b of a second portion of the same advancedpolishing pad. The first portion may be dispensed by a first print headaccording to the pixel chart 400 a and the second portion may bedispensed by a second print head according to the pixel chart 400 b. Thetwo print heads superimpose the pixel charts 400 a, 400 b together toform one or more layers that contain discrete polishing features. Thepolishing features near an edge region of the polishing pad include moreof the first material than the second material. The polishing featuresnear a center region of the polishing pad include more of the secondmaterial than the first material. In this example, each polishingfeature has a unique combination of the first material and the secondmaterial. In one example, the first polishing elements 204 include afirst combination of the first material and the second material and thesecond polishing elements 206 include a different second combination ofthe first material and the second material. Therefore, by use of pixelcharts, the polishing body can be sequentially formed so that a desiredgradient in material composition is achieved in different parts of thepolishing body to achieve a desired polishing performance of theadvanced polishing pad.

FIGS. 4C and 4D are schematic pixel charts 400 c, 400 d of a polishingpad having features. In some embodiments, FIG. 4C is the pixel chart 400c of a first portion of a polishing pad and FIG. 4D is the pixel chart400 d of a second portion of the same polishing pad. The polishing padaccording to FIGS. 4C, 4D is similar to the polishing pad of FIGS. 4A,4B except the gradient in the material composition of the polishing bodyvaries from left to right across the polishing pad.

FIG. 4E is a schematic view of a web based polishing pad 400 e that isformed using an additive manufacturing process to form a polishingsurface 208 that has a gradient in material composition across thepolishing surface 208 (e.g., Y-direction). As shown in FIG. 4E thepolishing material may be disposed over a platen 102 between a firstroll 481 and a second roll 482. By building a web, or even standardpolishing pad, with differing regions of high and low storage modulusthe substrate can be moved over different locations on the polishing pad400 e during different portion of the polishing process, so as toprovide the desired mechanical properties during each phase of thepolishing process. One example may involve a substrate having an initialsurface texture removed rapidly using a planarizing portion of thepolishing pad 400 e that has a high elastic modulus and then moving thesubstrate to a second portion of the polishing pad 400 e that has alower elastic modulus to buff the substrate surface and reduce scratchdefects.

FIG. 4F is schematic side cross-sectional view of an advanced polishingpad 400 f that is formed using an additive manufacturing process to forma polishing base layer 491 that has a gradient in material compositionin the Z-direction. Gradients in the material composition and/ormaterial properties of the stacked printed layers of the polishing baselayer 491 can vary from a high concentration to a low concentration of afirst material to a second material in one direction, or vice versa. Insome cases, one or more regions within the polishing pad may includemore complex concentration gradients, such as a high/low/high orlow/high/low concentration gradient of at least two materials that havediffering material properties. In one example, at least two materialsthat form the concentration gradient have different storage modulus E′,E′30/E′90 ratio, tan delta or other similar parameter. In someconfigurations, the advanced polishing pad 400 f may include a polishingelement region 494 that may include discrete regions that include atleast a first polishing element 204 and a second polishing element 206.In one example, the polishing element region 494 may include a portionof a polishing body 202 that contains one or more of the structuresshown in FIGS. 2A-2K.

In one embodiment, the base layer 491 includes a homogeneous mixture oftwo or more different materials in each layer formed within the baselayer 491. In one example, the homogeneous mixture may include a mixtureof the materials used to form the first polishing element 204 and thesecond polishing element 206 in each layer formed within the base layer491. In some configurations, it is desirable to vary the composition ofthe homogeneous mixture of materials layer by layer to form a gradientin material composition in the layer growth direction (e.g., Z-directionin FIG. 3B). The phrase homogeneous mixture is intended to generallydescribe a material that has been formed by dispensing and curingprinted droplets that have at least two different compositions withineach layer, and thus may contain a mixture of small regions of the atleast two different compositions that are each sized at a desiredresolution. The interface between the polishing base layer 491 and thepolishing element region 494 may include a homogeneous blend of thematerials found at the upper surface of the polishing base layer 491 andthe lower surface of the polishing element region 494, or include adiscrete transition where the differing material composition in thefirst deposited layer of the polishing element region 494 is directlydeposited on the surface of the polishing base layer 491.

In some embodiments of the polishing element region 494, or moregenerally any of the polishing bodies 202 described above, it isdesirable to form a gradient in the material composition in the firstpolishing elements 204 and/or second polishing elements 206 in adirection normal to the polishing surface of the polishing pad. In oneexample, it is desirable to have higher concentrations of a materialcomposition used to form the soft or low storage modulus E′ features inthe printed layers near the base of the polishing pad (e.g., opposite tothe polishing surface), and higher concentrations of a materialcomposition used to form the hard or high storage modulus E′ features inthe printed layers near the polishing surface of the polishing pad. Inanother example, it is desirable to have higher concentrations of amaterial composition used to form the hard or high storage modulus E′features in the printed layers near the base of the polishing pad, and ahigher concentration of a material composition used to form the soft orlow storage modulus E′ features in the printed layers near the polishingsurface of the polishing pad. Surface features use low storage modulusE′ can be used for defect removal and scratch reduction, and highstorage modulus E′ features can be used to enhance die and array scaleplanarization.

In one embodiment, it is desirable to form a gradient in the materialcomposition within the material used to form the first and/or secondpolishing elements in a direction normal to the polishing surface of thepolishing pad. In one example, it is desirable to have higherconcentrations of a material composition used to form the secondpolishing elements 206 in the printed layers near the base of thepolishing pad (e.g., opposite to the polishing surface), and higherconcentrations of a material composition used to form the firstpolishing elements 204 in the printed layers near the polishing surfaceof the polishing pad. In another example, it is desirable to have higherconcentrations of a material composition used to form the firstpolishing elements 204 in the printed layers near the base of thepolishing pad, and a higher concentration of a material composition usedto form the second polishing elements 206 in the printed layers near thepolishing surface of the polishing pad. For example, a first layer mayhave a material composition ratio of the first printed composition tothe second printed composition of 1:1, a material composition ratio ofthe first printed composition to the second printed composition of 2:1in a second layer and a material composition ratio of the first printedcomposition to the second printed composition of 3:1 in a third layer.In one example, the first printed composition has a higher storagemodulus E′ containing material than the second printed composition, andthe direction of sequential growth of the first, second and third layersis away from a supporting surface of the advanced polishing pad. Agradient can also be formed within different parts of a single layer byadjusting the placement of the printed droplets within the plane of thedeposited layer.

Advance Polishing Pad Formation Process Example

In some embodiments, the construction of an advanced polishing pad 200begins by creating a CAD model of the polishing pad design. This can bedone through the use of existing CAD design software, such asUnigraphics or other similar software. An output file, which isgenerated by the modelling software, is then loaded to an analysisprogram to ensure that the advanced polishing pad design meets thedesign requirements (e.g., water tight, mass density). The output fileis then rendered, and the 3D model is then “sliced” into a series of 2Ddata bitmaps, or pixel charts. As noted above, the 2D bitmaps, or pixelcharts, are used to define the locations across an X and Y plane wherethe layers in the advanced polishing pad will be built. In some additivemanufacturing process applications these locations will define where alaser will pulse, and in other applications the location where a nozzlewill eject a droplet of a material.

The coordinates found in the pixel charts are used to define thelocation at which a specific droplet of uncured polymer will be placedusing, for example, a poly jet print head. Every coordinate for an X andY location and a given pad supporting Z stage position will be definedbased on the pixel charts. Each X, Y and Z location will include eithera droplet dispense or droplet non-dispense condition. Print heads may beassembled in an array in the X and/or Y directions to increase buildrate or to deposit additional types of materials. In the examples shownin FIGS. 4A-4D, the black pixels indicate locations where nozzles willnot deposit materials and the white pixels indicate where nozzles willdeposit materials. By combining the material maps, or pixel charts, ineach formed layer a polishing pad of any desirable shape or structuralconfiguration can be printed by the positioning of the discrete dropletsnear one another.

An additive manufacturing device, such as a 3D printer can be used toform an advanced polishing pad by depositing thermoplastic polymers,depositing and curing of a photosensitive resin precursor compositions,and/or laser pulse type sintering and fusing of a dispensed powderlayer. In some embodiments, the advanced polishing pad formation processmay include a method of polyjet printing of UV sensitive materials. Inthis configuration, droplets of a precursor formulation (e.g., firstprintable ink composition 359) are ejected from a nozzle in the dropletejecting printer 306 and resin precursor composition is deposited ontothe build stage. As material is deposited from an array of nozzles, thematerial may be leveled with the use of a roller or other means tosmooth drops into a flat film layer or transfer away excess material.While the droplet is being dispensed, and/or shortly thereafter, a UVlamp or LED radiation source passes over the deposited layer to cure orpartially cure the dispensed droplets into a solid polymer network. Thisprocess is built layer on top of layer with adequate cohesion within thelayer and between layers to ensure the final embodiment of the pad modelis mechanically sound.

In order to better control the polymer stress through the build process,heat may be added during the formation of one or more of the layers. Thedelivery of heat allows the polymer network formed in each cured orpartially cured layer to relax and thereby reduce stress and removestress history in the film. Stress in the film can result in unwanteddeformation of the polishing pad during or after the polishing padformation process. Heating the partially formed polishing pad while itis on the printer's build tray ensures that the final pad properties areset through the layer by layer process and a predictable pad compositionand polishing result can be achieved. In addition to inducing heat intothe polishing pad formation process, the area surrounding the growingpolishing pad may be modified to reduce the oxygen exposure to theuncured resin. This can be done by employing vacuum or by flooding thebuild chamber with nitrogen (N₂) or other inert gas. The reduction inoxygen over the growing pad will reduce the inhibition of the freeradical polymerization reaction, and ensures a more complete surfacecure of the dispensed droplets.

Formulation and Material Examples

As discussed above, the materials used to form portions of the pad body202, such as the first polishing element 204 and second polishingelement 206 may each be formed from at least one ink jettablepre-polymer composition that may be a mixture of functional polymers,functional oligomers, reactive diluents, and curing agents to achievethe desired properties of an advanced polishing pad. In general, thepre-polymer inks or compositions may be processed after being depositedby use of any number of means including exposure or contact withradiation or thermal energy, with or without a curing agent or chemicalinitiator. In general, the deposited material can be exposed toelectromagnetic radiation, which may include ultraviolet radiation (UV),gamma radiation, X-ray radiation, visible radiation, IR radiation, andmicrowave radiation and also accelerated electrons and ion beams may beused to initiate polymerization reactions. For the purposes of thisdisclosure, we do not restrict the method of cure, or the use ofadditives to aid the polymerization, such as sensitizers, initiators,and/or curing agents, such as through cure agents or oxygen inhibitors.

In one embodiment, two or more polishing elements, such as the first andsecond polishing elements 204 and 206, within a unitary pad body 202,may be formed from the sequential deposition and post depositionprocessing of at least one radiation curable resin precursorcomposition, wherein the compositions contain functional polymers,functional oligomers, monomers, and/or reactive diluents that haveunsaturated chemical moieties or groups, including but not restrictedto: vinyl groups, acrylic groups, methacrylic groups, allyl groups, andacetylene groups. During the polishing pad formation process, theunsaturated groups may undergo free radical polymerization when exposedto radiation, such as UV radiation, in the presence of a curing agent,such as a free radical generating photoinitiator, such as an Irgacure®product manufactured by BASF of Ludwigshafen, Germany.

Two types of free radical photoinitiators may be used in one or more ofthe embodiments of the disclosure provided herein. The first type ofphotoinitiator, which is also referred to herein as a bulk curephotoinitiator, is an initiator which cleaves upon exposure to UVradiation, yielding a free radical immediately, which may initiate apolymerization. The first type of photoinitiator can be useful for bothsurface and through or bulk cure of the dispensed droplets. The firsttype of photoinitiator may be selected from the group including, but notrestricted to: benzoin ethers, benzyl ketals, acetyl phenones, alkylphenones, and phosphine oxides. The second type of photoinitiator, whichis also referred to herein as a surface cure photoinitiator, is aphotoinitiator that is activated by UV radiation and forms free radicalsby hydrogen abstraction from a second compound, which becomes the actualinitiating free radical. This second compound is often called aco-initiator or polymerization synergist, and may be an amine synergist.Amine synergists are used to diminish oxygen inhibition, and therefore,the second type of photoinitiator may be useful for fast surface cure.The second type of photoinitiator may be selected from the groupincluding but not restricted to benzophenone compounds and thioxanthonecompounds. An amine synergist may be an amine with an active hydrogen,and in one embodiment an amine synergist, such as an amine containingacrylate may be combined with a benzophenone photoinitiator in a resinprecursor composition formulation to: a) limit oxygen inhibition, b)fast cure a droplet or layer surface so as to fix the dimensions of thedroplet or layer surface, and c), increase layer stability through thecuring process. In some cases, to retard or prevent free radicalquenching by diatomic oxygen, which slows or inhibits the free radicalcuring mechanism, one may choose a curing atmosphere or environment thatis oxygen limited or free of oxygen, such as an inert gas atmosphere,and chemical reagents that are dry, degassed and mostly free of oxygen.

It has been found that controlling the amount of the chemical initiatorin the printed formulation is an important factor in controlling theproperties of a formed advanced polishing pad, since the repeatedexposure of underlying layers to the curing energy as the advancedpolishing pad is formed will affect the properties of these underlyinglayers. In other words, the repeated exposure of the deposited layers tosome amount of the curing energy (e.g., UV light, heat, etc.) willaffect the degree of cure, or over curing the surface of that layer,within each of the formed layers. Therefore, in some embodiments, it isdesirable to ensure that the surface cure kinetics are not faster thanthrough-cure (bulk-cure), as the surface will cure first and blockadditional UV light from reaching the material below the surface curedregion; thus causing the overall partially cured structure to be“under-cured.” In some embodiments, it is desirable to reduce the amountof photoinitiator to ensure proper chain extension and cross linking. Ingeneral higher molecular weight polymers will form with a slowercontrolled polymerization. It is believed that if the reaction productscontain too many radicals, reaction kinetics may proceed too quickly andmolecular weights will be low which will in turn reduce mechanicalproperties of the cured material.

In some embodiments, the first and second polishing elements 204 and 206may contain at least one oligomeric and/or polymeric segments,compounds, or materials selected from: polyamides, polycarbonates,polyesters, polyether ketones, polyethers, polyoxymethylenes, polyethersulfone, polyetherimides, polyimides, polyolefins, polysiloxanes,polysulfones, polyphenylenes, polyphenylene sulfides, polyurethanes,polystyrene, polyacrylonitriles, polyacrylates, polymethylmethacrylates,polyurethane acrylates, polyester acrylates, polyether acrylates, epoxyacrylates, polycarbonates, polyesters, melamines, polysulfones,polyvinyl materials, acrylonitrile butadiene styrene (ABS), halogenatedpolymers, block copolymers and copolymers thereof. Production andsynthesis of the compositions used to form the first polishing element204 and second polishing element 206 may be achieved using at least oneUV radiation curable functional and reactive oligomer with at least oneof the aforementioned polymeric and/or molecular segments, such as thatshown in chemical structure A:

The difunctional oligomer as represented in chemical structure A,bisphenol-A ethoxylate diacrylate, contains segments that may contributeto the low, medium, and high storage modulus E′ character of materialsfound in the first polishing element 204 and second polishing element206 in the pad body 202. For example, the aromatic groups may impartadded stiffness to pad body 202 because of some local rigidity impartedby the phenyl rings. However, those skilled in the art will recognizethat by increasing the ether chain segment “n” will lower the storagemodulus E′ and thus produce a softer material with increasedflexibility. In one embodiment, a rubber-like reactive oligomer,polybutadiene diacrylate, may be used to create a softer and moreelastic composition with some rubber-like elastic elongation as shown inchemical structure B:

Polybutadiene diacrylate includes pendant allylic functionality (shown),which may undergo a crosslinking reaction with other unreacted sites ofunsaturation. In some embodiments, the residual double bonds in thepolybutadiene segment “m” are reacted to create crosslinks which maylead to reversible elastomeric properties. In one embodiment, anadvanced polishing pad containing compositional crosslinks may have apercent elongation from about 5% to about 40%, and a E′30:E′90 ratio ofabout 6 to about 15. Examples of some crosslinking chemistries includesulfur vulcanization and peroxide, such as tert-butyl perbenzoate,dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide and the like.In one embodiment, 3% benzoyl peroxide, by total formulation weight, isreacted with polybutadiene diacrylate to form crosslinks such that thecrosslink density is at least about 2%.

Chemical structure C represents another type of reactive oligomer, apolyurethane acrylate, a material that may impart flexibility andelongation to the advanced polishing pad. An acrylate that containsurethane groups may be an aliphatic or an aromatic polyurethaneacrylate, and the R or R′ groups shown in the structure may bealiphatic, aromatic, oligomeric, and may contain heteroatoms such asoxygen.

Reactive oligomers may contain at least one reactive site, such as anacrylic site, and may be monofunctional, difunctional, trifunctional,tetrafunctional, pentafunctional and/or hexafunctional and thereforeserve as foci for crosslinking. FIG. 5B is a plot of stress vs. strainfor some cured reactive oligomers that may be useful for creating 3Dprintable ink compositions. The oligomers may represent “soft” or a lowstorage modulus E′ materials, “medium soft” or medium storage modulus E′materials, or “hard” or high storage modulus E′ materials (e.g., Table1). As shown, the storage modulus E′ (e.g., slope, or Δy/Δx) increasesfrom a soft and flexible and stretchable polyurethane acrylate to anacrylic acrylate, then to a polyester acrylate, and then to the hardestin the series, a hard and high storage modulus E″ epoxy acrylate. FIG.5B illustrates how one may choose a storage modulus E′ material, or arange or mixture of storage modulus E′ materials, that may be useful forproduction of an advanced polishing pad. Functional oligomers may beobtained from a variety of sources including Sartomer USA of Exton, Pa.,Dymax Corporation of Torrington, Conn., USA, and Allnex Corporation ofAlpharetta, Ga., USA.

In embodiments of the disclosure, multifunctional acrylates, includingdi, tri, tetra, and higher functionality acrylates, may be used tocreate crosslinks within the material used to form, and/or between thematerials found in, the first polishing element 204 and second polishingelement 206, and thus adjust polishing pad properties including storagemodulus E′, viscous dampening, rebound, compression, elasticity,elongation, and the glass transition temperature. It has been found thatby controlling the degree of crosslinking within the various materialsused to form the first polishing element 204 and second polishingelement 206 desirable pad properties can be formed. In someconfigurations, multifunctional acrylates may be advantageously used inlieu of rigid aromatics in a polishing pad formulation, because the lowviscosity family of materials provides a greater variety of moleculararchitectures, such as linear, branched, and/or cyclic, as well as abroader range of molecular weights, which in turn widens the formulationand process window. Some examples of multifunctional acrylates are shownin chemical structures D (1,3,5-triacryloylhexahydro-1,3,5-triazine),and E (trimethylolpropane triacrylate):

The type or crosslinking agent, chemical structure, or the mechanism(s)by which the crosslinks are formed are not restricted in the embodimentsof this disclosure. For example, an amine containing oligomer mayundergo a Michael addition type reaction with acrylic moiety to form acovalent crosslink, or an amine group may react with an epoxide group tocreate a covalent crosslink. In other embodiments, the crosslinks may beformed by ionic or hydrogen bonding. The crosslinking agent may containlinear, branched, or cyclic molecular segments, and may further containoligomeric and/or polymeric segments, and may contain heteroatoms suchas nitrogen and oxygen. Crosslinking chemical compounds that may beuseful for polishing pad compositions are available from a variety ofsources including: Sigma-Aldrich of St. Louis, Mo., USA, Sartomer USA ofExton, Pa., Dymax Corporation of Torrington, Conn., USA, and AllnexCorporation of Alpharetta, Ga., USA.

As mentioned herein, reactive diluents can be used as viscosity thinningsolvents that are mixed with high viscosity functional oligomers toachieve the appropriate viscosity formulation, followed bycopolymerization of the diluent(s) with the higher viscosity functionaloligomers when exposed to a curing energy. In one embodiment, when n˜4,the viscosity of bisphenol-A ethoxylate diacrylate may be about 1350centipoise (cP) at 25° C., a viscosity which may be too high to effectdispense of a such a material in a 3D printing process. Therefore, itmay be desirable to mix bisphenol-A ethoxylate diacrylate with a lowerviscosity reactive diluents, such as low molecular weight acrylates, tolower the viscosity to about 1 cP to about 100 cP at 25° C., such asabout 1 cP to about 20 cP at 25° C. The amount of reactive diluent useddepends on the viscosity of the formulation components and thediluent(s) themselves. For example, a reactive oligomer of 1000 cP mayrequire at least 40% dilution by weight of formulation to achieve atarget viscosity. Examples of reactive diluents are shown in chemicalstructures F (isobornyl acrylate), G (decyl acrylate), and H (glycidylmethacrylate):

The respective viscosities of F-G at 25° C. are 9.5 cP, 2.5 cP, and 2.7cP, respectively. Reactive diluents may also be multifunctional, andtherefore may undergo crosslinking reactions or other chemical reactionsthat create polymer networks. In one embodiment, glycidyl methacrylate(H), serves as a reactive diluent, and is mixed with a difunctionalaliphatic urethane acrylates, so that the viscosity of the mixture isabout 15 cP. The approximate dilution factor may be from about 2:1 toabout 10:1, such as about 5:1. An amine acrylate may be added to thismixture, such as dimethylaminoethyl methacrylate, so that it is about10% by weight of the formulation. Heating the mixture from about 25° C.to about 75° C. causes the reaction of the amine with the epoxide, andformation of the adduct of the acrylated amine and the acrylatedepoxide. A suitable free radical photoinitiator, such as Irgacure® 651,may be then added at 2% by weight of formulation, and the mixture may bedispensed by a suitable 3D printer so that a 20 micron thick layer isformed on a substrate. The layer may then be cured by exposing thedroplet or layer for between about 0.1 μs to about 10 seconds, such asabout 0.5 seconds, to UV light from about 200 nm to about 400 nm using ascanning UV diode laser at an intensity of about 10 to about 50 mJ/cm²to create a thin polymer film. Reactive diluent chemical compounds thatmay be useful for 3D printed polishing pad compositions are availablefrom a variety of sources including Sigma-Aldrich of St. Louis, Mo.,USA, Sartomer USA of Exton, Pa., Dymax Corporation of Torrington, Conn.,USA, and Allnex Corporation of Alpharetta, Ga., USA.

Another method of radiation cure that may be useful in the production ofpolishing pads is cationic cure, initiated by UV or low energy electronbeam(s). Epoxy group containing materials may be cationically curable,wherein the ring opening polymerization of epoxy groups may be initiatedby cations such as protons and Lewis acids. The epoxy materials may bemonomers, oligomers or polymers, and may have aliphatic, aromatic,cycloaliphatic, arylaliphatic or heterocyclic structures; and they canalso include epoxide groups as side groups or groups that form part ofan alicyclic or heterocyclic ring system.

UV-initiated cationic photopolymerization exhibits several advantagescompared to the free-radical photopolymerization including lowershrinkage, better clarity, better through cure via livingpolymerization, and the lack of oxygen inhibition. UV cationicpolymerization may polymerize important classes of monomers which cannotbe polymerized by free radical means, such as epoxides, vinyl ethers,propenyl ethers, siloxanes, oxetanes, cyclic acetals and formals, cyclicsulfides, lactones and lactams. These cationically polymerizablemonomers include both unsaturated monomers, such as glycidylmethacrylate (chemical structure H) that may also undergo free-radicalpolymerization through the carbon-carbon double bonds as describedherein. Photoinitiators that generate a photoacid when irradiated withUV light (˜225 to 300 nm) or electron beams include, but are not limitedto aryl onium salts, such as iodonium and sulfonium salts, such astriarylsulfonium hexafluorophosphate salts, which may be obtained fromBASF of Ludwigshafen, Germany (Irgacure® product).

In one embodiment, the material(s) used to form the first polishingelement 204 and the second polishing element 206, and thus the unitarypad body 202, may be formed from the sequential deposition and cationiccure of at least one radiation curable resin precursor composition,wherein the compositions contain functional polymers, functionaloligomers, monomers, and/or reactive diluents that have epoxy groups.Mixed free radical and cationic cure systems may be used to save costand balance physical properties. In one embodiment, the first polishingelement 204 and the second polishing element 206, may be formed from thesequential deposition and cationic and free radical cure of at least oneradiation curable resin precursor composition, wherein the compositionscontain functional polymers, functional oligomers, monomers, reactivediluents that have acrylic groups and epoxy groups. In anotherembodiment, to take advantage of the clarity and lack of lightabsorption inherent in some cationically cured systems, an observationwindow or CMP end-point detection window, which is discussed furtherbelow, may be formed from a composition cured by the cationic method. Insome embodiments, some of the layers in the formed advanced polishingpad may be formed by use of a cationic curing method and some of thelayers may be formed from a free radical curing method.

In one embodiment, the 3D printed polymer layers may contain inorganicand/or organic particles that are used to enhance one or more padproperties of selected material layers found in the formed advancedpolishing pad 200. Because the 3D printing process involves layer bylayer sequential deposition of at least one composition per layer, itmay also be desirable to additionally deposit inorganic or organicparticles disposed upon or within a pad layer to obtain a certain padproperty and/or to perform a certain function. The inorganic or organicparticles may be in the 25 nanometer (nm) to 100 micrometer (μm) rangein size and may be added to the precursor materials prior to beingdispensed by the droplet ejecting printer 306 or added to an uncuredprinted layer in a ratio of between 1 and about 50 weight percent (wt%). The inorganic or organic particles may be added during the advancedpolishing pad formation process to improve the ultimate tensilestrength, improve yield strength, improve the stability of the storagemodulus over a temperature range, improve heat transfer, adjust asurfaces zeta potential, and/or adjust a surface's surface energy. Theparticle type, chemical composition, or size, and the added particlesmay vary by application or desired effect that is to be achieved. Insome embodiments, the particles may include intermetallics, ceramics,metals, polymers and/or metal oxides, such as ceria, alumina, silica,zirconia, nitrides, carbides, or a combination thereof. In one example,the inorganic or organic particles disposed upon, over or within a padmay include particles of high performance polymers, such PEEK, PEK, PPS,and other similar materials to improve the mechanical properties and/orthermal conductivity of the advanced polishing pad. The particles thatare integrated in a 3D printed polishing pad may also serve as foci forcrosslinking, which may lead to a higher storage modulus E′ depending ona percent by weight loading. In another example, a polymer compositioncontaining polar particles, such as ceria, may have a further affinityfor polar materials and liquids at the pad surface, such as CMPslurries.

Advanced Polishing Pad Properties

An advantage of forming an advanced polishing pad 200 that has a padbody 202 that includes at least a first polishing element 204 and asecond polishing element 206 is the ability to form a structure that hasmechanical, structural and dynamic properties that are not found in apad body that is formed from a single material composition. In someembodiments, it is desirable to form a polishing body 202 that includesat least one region in which the first polishing element 204 is disposedover and supported by a portion (e.g., portion 212A in FIG. 2A) of thesecond polishing element 206. In this configuration, the combination ofthe properties of the two materials and structural configuration can beused to form an advanced polishing pad that has desirable mechanical,structural and dynamic properties, and improved polishing performanceover conventional polishing pad designs.

Materials and chemical structure of the materials in the first polishingelement(s) 204 and/or the second polishing element(s) 206 may beselected to achieve a “tuned” bulk material by use of the aforementionedchemistries. An advanced polishing pad 200 formed with this “tuned” bulkmaterial has various advantages, such as improved polishing results,reduced cost of manufacturing, and elongated pad life. In oneembodiment, an advanced polishing pad 200, when measured as a whole, mayhave a hardness between about 25 shore A to about 75 shore D, a tensilestrength of between 5 MPa and about 75 MPa, an elongation at break ofbetween about 5% and about 350%, a shear strength of above about 10 MPa,and a storage modulus E′ modulus between about 5 MPa and about 3000 MPa.

As discussed above, materials having different mechanical properties maybe selected for use in the first polishing element 204 and/or secondpolishing element 206 to achieve an improved polishing result on apolished substrate. The mechanical properties, such as storage modulusE′ of the material(s) found in the formed first polishing element 204and/or second polishing element 206, may be created by selectingdifferent materials, material compositions and/or choosing differentpost deposition processing steps (e.g., curing processes) used duringthe polishing element forming process. In one embodiment, the secondpolishing element 206 may have a lower hardness value and a lower valueof storage modulus E′, while the first polishing element 204 may have ahigher hardness value and a higher value of storage modulus E′. Inanother embodiment, storage modulus E′ may be adjusted within eachpolishing element 204, 206 and/or at various different locations acrossthe polishing surface of the polishing pad. In one embodiment, the firstpolishing elements 204 may have a hardness of about 40 Shore D scale toabout 90 Shore D scale. The second polishing element 206 may have ahardness value between about 26 Shore A scale to about 95 Shore A scale.The first polishing element 204 and second polishing element 206 mayeach include different chemical compositions that are co-mingled andchemically bounded together at multiple boundaries within the unitarypad body 202.

For the purposes of this disclosure, and without intending to limit thescope of the disclosure provided herein, materials having desirable low,medium, and/or high storage modulus E′ properties at temperatures of 30°C. (E′30) and 90° C. (E′90) for the first polishing elements 204 and thesecond polishing elements 206 in an advanced polishing pad 200, aresummarized in Table 2:

TABLE 2 Low Storage Medium High Storage Modulus Storage Modulus ModulusCompositions Compositions Compositions E′30 5 MPa-100 MPa 100 MPa-500MPa 500 MPa-3000 MPa E′90 <17 MPa <83 MPa <500 MPa

In one embodiment of an advanced polishing pad 200, a plurality of firstpolishing elements 204 are configured to protrude above one or moresecond polishing elements 206, so that during a polishing process thesurface of a substrate 110 is polished using the polishing surface 208of the first polishing elements 204. In one embodiment, to assure that adesirable planarity, polishing efficiency, and reduced dishing during abulk material polishing step it is desirable to form the first polishingelements 204, which contact the surface of the substrate during thepolishing process, with a material that has a high storage modulus E′,such as defined in Table 2. However, in one embodiment, to assure that adesirable planarity, polishing efficiency, and reduced dishing during abuffing or residual material clearing step it may be desirable to formthe first polishing elements 204, which contact the surface of thesubstrate during the polishing process, with a material that has a lowor medium storage modulus E′.

In some embodiments, the storage modulus of the first polishing elements204 is adjusted to minimize the effect of pad glazing, which cause thepolishing process removal rates to reduce over time in the absence of aprocess of abrading the glazed surface of the used polishing pad (i.e.,pad conditioning). It is believed that pad glazing is caused by theplastic deformation of the materials that contact the surface of thesubstrate, which is inversely proportional to the shear modulus (G′) asshear forces on the pad surface cause the “cold flow” or plasticdeformation of the contacting material. For an isotropic solid, theshear modulus is generally related to the storage modulus by thefollowing equation: G′=E′/2(1+v), where v is Poison's ratio. Thus, thematerials used to form the first polishing elements 204 that have a lowshear modulus, and thus storage modulus, would have a faster rate ofplastic deformation and thus formation of glazed areas. Therefore, it isalso desirable to form the first polishing elements 204 with a materialthat has a high storage modulus E′ and/or hardness, as defined above.

To assure that a glazed surface of a polishing pad can be rejuvenated byuse of a pad conditioning process, it is also desirable for thematerial(s) used to form the first polishing elements 204 to havedesirable tensile strength and percent elongation at fracture. In someembodiments, the ultimate tensile strength (UTS) of the material used toform the first polishing elements 204 is between about 250 psi and 9,000psi. It is believed that the higher the UTS of the material used to formthe first polishing elements 204 the more durable and less particulateformation prone the polishing pad material will be before, during orafter performing the pad conditioning process. In one example, the UTSof the material used to form the first polishing elements 204 is betweenabout 5,000 psi and about 9,000 psi. In some embodiments, the elongationat fracture of the material used to form the first polishing elements204 is between about 5% and 200%. It is believed that the lower theelongation at fracture of the material used to form the first polishingelements 204 the less deformable the material will be, and thus theeasier to maintain the surface micro-texture or asperities which allowfor abrasive capture and slurry transport. In one embodiment, theelongation at fracture of the material used to form the first polishingelements 204 that is configured to touch the polished surface of asubstrate is adjusted to be between about 5% and about 40%.

There is a need to also provide a polishing pad that has desirabledampening properties to reduce the elastic rebound of a pad duringpolishing, which can cause dishing and other negative attributesrelating to the cyclic deformation of the pad during processing.Therefore, to compensate for the need for a high storage modulus E′material to contact the surface of the substrate during polishing, thesecond polishing element 206, which is positioned to support the firstpolishing element 204, is formed from a material that has lower storagemodulus E′.

In one example, an advanced polishing pad 200 may include the tan δproperties illustrated in FIG. 5A. FIG. 5A includes tan δ data (1 Hz,ramp rate 5° C./min) for a first polishing pad material (e.g., curve591), a second polishing pad material (e.g., curve 592), and an advancedpolishing pad configuration (e.g., curve 593) that contains regions thatinclude either the first polishing pad material (e.g., soft material) orthe second polishing pad material (e.g., hard material). As illustrated,the tan δ data contains separate and discrete tan δ peaks for the firstand second materials, as shown by curves 591 and 592. In contrast thetan δ peaks for the advanced polishing pad material, curve 593, arebroadened and coalesced, which is indicative of molecular scale mixing,chain entanglement, chemical bonding and/or a compositional gradientbetween the first polishing pad material, such as found in a secondpolishing element 206, and the second polishing pad material, such asfound in a first polishing element 204. It has been found that a tan δmaximum of between about 0.1 and about 3 between a temperature of 30° C.and 90° C. is useful to minimize the amount of dishing, planarizationefficiency and other related polishing non-uniformity.

In an effort to further control process repeatability, another parameterthat can be controlled in an advanced polishing pad is a pad material's“recovery.” FIG. 5C illustrates a plot of storage modulus E′ as afunction of temperature taken over a number of simulated polishingcycles for a material that may form part of the first polishing elements204 or the second polishing element 206. The plot 580 includes aplurality of curves that measure the drop in storage modulus E′ from aninitial starting storage modulus value 576 as the polishing pad heats upfrom a starting temperature of about 30° C. to a final steady statepolishing temperature about 90° C. (e.g., storage modulus value 588),and as the pad cools down from about 90° C. to a final temperature about30° C. during each polishing cycle. For illustration purposes andclarity of discussion the plot in FIG. 5C illustrates data for threepolishing cycles, which includes a first polishing cycle that includescurves 582 and 583, a second polishing cycle that includes curves 584and 585 and a third polishing cycle that includes curves 586 and 587. Asshown in FIG. 5C, at the end of each cycle 577-579 there is a drop inthe measured storage modulus due to relaxation of the stress found inthe polishing pad material and/or at least partial reconfiguration ofbonding structure of the polymeric materials that likely occurs at thehigher polishing temperatures when a higher load is applied during thepolishing process. How well a material recovers after a number ofsuccessive cycles is known as a material's ability to “recover.”Recovery is typically measured as a percentage of the drop in themagnitude of a property of a material (e.g., storage modulus) from thestarting point 576 to a stable equilibrium point 579 that is measured atthe same point in a polishing cycle. Recovery can be calculated bymeasuring the ratio of the ending value 589 to the starting value 590times a hundred. To assure polishing process stability, it is generallydesirable for the recovery of the materials in a polishing pad to be aslarge as possible, and thus it is believed that the recovery needs to beat least greater than 50%, or even greater than or equal to about 70%using a dynamic mechanical analysis (DMA) test that is configured tosimulate a CMP process. In one example, the DMA test is between about5-10 minutes long, such as about 8 minutes long, and the maximumtemperature ramp rate is about 5° C./min, which is intended to simulatea standard CMP process. The DMA test is used to emulate pad heatingwhich takes place on the polisher due to friction between the substrate,slurry, retaining ring, and polishing pad. Heat tends to build upthrough the polishing run and is then rapidly quenched between substrateprocessing steps, due to normal fluid convection or conduction of heataway from the pad. In some embodiments, to assure the polishing pad hasa desirable recovery, and thus assure that the polishing process isstable, it is desirable to adjust the composition of the precursorformulation and/or curing process parameters to control the stress inthe formed layer and/or degree of cross linking. In some embodiments, itmay also be desirable to anneal the advanced polishing pad prior to usein a polishing process.

It is also believed that to maintain optimal polishing uniformity andpolishing performance on a substrate, the E′30:E′90 ratio of the padmaterials should be controlled and adjusted as needed. To that end, inone embodiment, the E′30:E′90 ratio of the one or more of the formed padmaterials (e.g., material used to form first polishing element 204),and/or the overall advanced polishing pad 200, may be greater than orequal to 6, such as between about 6 and about 15. The polishing pad mayhave a stable storage modulus E′ over a temperature range of about 25°C. to about 90° C. such that storage modulus E′ ratio at E′30/E′90 fallswithin the range between about 6 to about 30, wherein E′30 is thestorage modulus E′ at 30° C. and E′90 is the storage modulus E′ at 90°C. Polishing pads that have an E′30:E′90 ratio that is 6 or higher areuseful to reduce scratch type defects often created when using highstorage modulus E′ materials at temperatures that are below steady stateprocessing temperatures seen during normal processing. In other words,as the temperature rises in the materials, which are in contact with thesubstrate during processing, the materials will tend to soften a largerextent than materials having a lower E′30:E′90 ratio, which will thustend to reduce the possibility of scratching the surface of thesubstrate. The material softening through the polish process can impactthe substrate-to-substrate stability of the process in unfavorable ways.However, high E′30:E′90 ratio materials may be useful where the initialportion (e.g., 10-40 seconds) of a polish process needs a high storagemodulus in the polishing surface materials, and then as the temperaturecontinues to increase to levels in which the polishing surface materialsbecome compliant, the polishing surface materials finish the polishingprocess in a buff or scratch reducing mode.

In some embodiments, it is desirable to control the thermal conductivityof various sections of the advanced polishing pad to allow for thecontrol one or more aspects of the polishing process. In one embodiment,it is desirable to increase the thermal conductivity of the overalladvanced polishing pad in a direction normal to the polishing surface,such as the Z-direction in FIGS. 1A-2K. In this example, the increasedthermal conductivity in the Z-direction, over traditional polishing padformulations, allows the polishing pad surface temperature to bemaintained at a lower temperature, due the ability to more easilyconduct the heat generated at the polishing pad surface duringprocessing to the large thermal mass and/or often cooled polishingplaten on which the advanced polishing pad is positioned. The reducedpolishing process temperature will reduce the polishing processvariability often seen when polishing a first substrate in a batch ofsubstrates versus the last substrate in the batch (e.g., 25^(th)substrate), and reduce the degradation of material properties oftenfound in polymeric materials (e.g., storage modulus E′, E′ ratio, etc.)over the batch of substrates. Alternately, in some embodiments, it isdesirable to reduce the thermal conductivity of the overall advancedpolishing pad in a direction normal to the polishing surface, such asthe Z-direction in FIG. 1A. In this case, the reduced thermalconductivity in the Z-direction, over traditional polishing padformulations, allows the polishing pad surface temperature to rapidlyrise to an equilibrium processing temperature during polishing, due thereduced ability of the polishing pad to conduct the heat generated atthe polishing pad surface during processing to the polishing platen onwhich the advanced polishing pad is positioned. The often higher, butmore stable, polishing process temperatures can also be used to reducethe polishing process variability often seen when polishing a firstsubstrate in a batch of substrates versus the last substrate in thebatch (e.g., 25^(th) substrate).

Therefore, in some embodiments, it is desirable to add one or morefillers, particles or other materials to the first polishing elements204 and/or second polishing element(s) 206 during the formation processto adjust the thermal conductivity of the advanced polishing pad 200 inthe any direction (e.g., X, Y or Z-directions) within the polishing padby use of one or more of the additive manufacturing process describedherein. The thermal conductivity of polymers has been traditionallyenhanced by the addition of thermally conductive fillers, includinggraphite, carbon black, carbon fibers, and nitrides, so a polishing padformulation and composition may contain thermally conductive particlesand compounds such as boron nitride, to increase the thermalconductivity of a polishing pad. For example, a conventional polishingpad without a thermally conductive filler may have a thermalconductivity of about 0.1 W/m·K to about 0.5 W/m·K at 25° C. In oneembodiment, boron nitride, with a thermal conductivity of about 250W/m·K is added to a polishing pad, at about 10 wt % based onformulation. The layers containing boron nitride may be deposited atand/or near the pad surface that contacts the substrate being polished,and that may be subjected to the most heating due to frictionalpolishing forces generated during polishing. In one embodiment, theadditional boron nitride particles increased the thermal conductivity ofthe polishing pad from about 10% to about 25%, and thus increased thelife of the polishing pad by about two times. In another embodiment,polymer layers at or near the polishing surface, such as first polishingelement 204, may contain particles that aid in the removal of substratemetals and/or metal oxides.

In one embodiment, a percent by weight of silica particles in thesurface layers may be from about 0.1% to about 30% by weight offormulation, such as 10% by weight, and by which may increase the Shorehardness and modulus of such a coating from about 10% to about 50%. Inone embodiment, the particle surface may be chemically modified so thatthe particles may be well mixed and/or suspended in a 3D polishing padink, and thus more easily dispensed, without phase separation. Chemicalmodifications include the chemical binding of surfactant like moleculesto the polar surface of a particle by a “coupling agent, such as asilane coupling agent. Other coupling agents that may be useful includetitanates and zirconates. The chemical binding, coupling, or attachmentof a coupling agent to a particle may occur by chemical reactions suchas hydrolysis and condensation. Coupling agents and related chemicalcompounds described herein are available from a number of sources,including Gelest Incorporated of Morrisville, Pa., USA, andSigma-Aldrich Chemical Company, of St. Louis, Mo., USA.

In one embodiment, the unitary pad body 202 may have pores that containair or another gas. The pores may be generated by radiation or thermallyinduced generation of gaseous materials. In one embodiment, an advancedpolishing pad pre-polymer composition may contain compounds, polymers,or oligomers that are thermally labile and that may contain of thermallylabile groups. The porogens and thermally labile groups may be cyclicgroups, such as unsaturated cyclic organic groups. The porogen maycomprise a cyclic hydrocarbon compound. Some exemplary porogens include,but are not restricted to: norbornadiene (BCHD,bicycle(2.2.1)hepta-2,5-diene), alpha-terpinene (ATP), vinylcyclohexane(VCH), phenylacetate, butadiene, isoprene, and cyclohexadiene. In oneembodiment, a pre-polymer layer is deposited that contains a radiationcurable oligomer with a covalently bound porogen group. After exposureto UV radiation and heat, a porous polymer layer may be formed by theeffusion of the porogen group. In another embodiment, a plurality ofporous layers may be formed by sequential layer deposition and poreformation. In other embodiments, pores may be generated by thermallyinduced decomposition of compounds that form a gas by-product, such asazo compounds, which decompose to form nitrogen gas.

Advanced Polishing Pad Formulation Examples

As noted above, in some embodiments, one or more of the materials thatare used to form at least one of the two or more polishing elements,such as the first and second polishing elements 204 and 206, is formedby sequentially depositing and post deposition processing of at leastone curable resin precursor composition. In general, the curable resinprecursor compositions, which are mixed during the precursor formulationprocess performed in the precursor delivery section 353 of the additivemanufacturing system 350, will include the formulation of resinprecursor compositions that contain functional oligomers, reactivediluents and curing components, such as initiators. Examples of some ofthese components are listed in Table 3.

TABLE 3 Reference Tg UTS Name Material Information Functionality (° C.)(psi) % Elongation O1 Aliphatic urethane 2 27 5378 79 acrylate oligomerO2 Aliphatic hexafunctional 6 145 11,000 1 urethane acrylate O3 Lowviscosity diacrylate 2 26 1,600 10 oligomer O4 Aliphatic hexafunctional6 120 acrylate O5 Multifunctional urethane 3.4 46 3045 2 acrylateoligomer M1 Dipropylene glycol 2 104 2938 5 diacrylate M2 2-Propenoicacid, 2- 1 5 19 236 phenoxyethyl ester M3 Tertio-butyl 1 41 cyclohexanolacrylate (TBCHA) M4 Polyether-modified polydimethylsiloxane M5 CTFA 2Ethers 1 32 — — M6 EOEO-EA 1 −54 — — P1 2-Hydroxy-2-methyl-1- N/A N/AN/A phenyl-propan-1-one P2 4-Phenylbenzophenone N/A N/A N/A A1 Acrylatedamine <1 N/A N/A N/A synergistExamples of functional oligomers can be found in items O1-O5 in Table 3.Examples of functional reactive diluents and other additives can befound in items M1-M6 in Table 3. Examples of curing components are foundin items P1-P2 and A1 in Table 3. Items O1-O3, M1-M3 and M5-M6 found inTable 3 are available from Sartomer USA, item O4 is available from MiwonSpecialty Chemicals Corporation of Korea, item O5 is available fromAllnex Corporation of Alpharetta, Ga., USA, item M4 is available fromBYK-Gardner GmbH of Germany and items P1-P2 and A1 are available fromChiba Specialty Chemicals Inc. and RAHN USA Corporation.

One advantage of the additive manufacturing processes described hereinincludes the ability to form an advance polishing pad that hasproperties that can be adjusted based on the composition of thematerials and structural configuration of the various materials usedwithin the pad body structure. The information below provides someexamples of some material formulations and the affect that varyingvarious components in these formulations and/or processing techniqueshave on some of the properties needed to form an advanced polishing padthat will achieve improved polishing results over conventional polishingpad designs. The information provided in these examples can be used toform at least a portion of the advanced polishing pad 200, such as partof the first polishing element 204, the second polishing element 206, orboth the first and second polishing elements 204 and 206. The examplesprovided herein are not intended to be limiting as to the scope of theinvention provided herein, since other similar chemical formulations andprocessing techniques can be used to adjust some of the propertiesdescribed herein.

Examples of the curable resin precursor composition components, whichare described above and below, are intended to be comparative examplesand one skilled in the art can find other suitable monomers/oligomersfrom various sources to achieve the desired properties. Some examplesfor reactive diluents are 2-ethylhexyl acrylate, octyldecyl acrylate,cyclic trimethylolpropane formal acrylate, caprolactone acrylate andalkoxylated lauryl methacrylate. The first material is available fromSigma-Aldrich, and the balance may be obtained from Sartomer USA and/orRahn AG USA (SR series 203, 217, 238, 242, 306, 339, 355, 368, 420, 484,502, 506A, 508, SR 531, 550, 585, 495B, 256, 257, 285, 611, 506, 833S,and 9003B, CD series 421A, 535, 545, 553, 590, 730, and 9075, Genomerseries 1116, 1117, 1119, 1121, 1122, 5142, 5161, 5275, 6058, 7151, and7210, Genocure series, BP, PBZ, PMP, DETX, ITX, LBC, LBP, TPO, andTPO-L, and Miramer series, M120, M130, M140, M164, M166, and M170). Someexamples for difunctional cross-linkers are bisphenol A glycerolatedimethacrylate, ethylene glycol dimethacrylate, diethylene glycoldimethacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanedioldiacrylate and 1,4-butanediol diacrylate, which may be obtained fromSigma-Aldrich. Some examples of oligomers could include aliphaticoligomers (CN series 131, 131B, 132, 152, 508, 549, 2910, 3100 and 3105from Sartomer USA), polyester acrylate oligomers (CN series 292, 293,294E, 299, 704, 2200, 2203, 2207, 2261, 2261 LV, 2262, 2264, 2267, 2270,2271E, 2273, 2279, 2282, 2283, 2285 and 2303 from Sartomer USA) andaliphatic urethane oligomers (CN series 929, 959, 961 H81, 962, 969,964A85, 965, 968, 980, 986, 989, 991, 992, 996, 2921, 9001, 9007, 9013,9178 and 9783 from Sartomer USA). The agents or additives could besupplied from BYK, such as 3550, 3560, 307, 378, 1791, 1794, 9077, A515,A535, JET9510, JET9511, P9908, UV3500, UV3535, DISPERBYK168, andDISPERBYK2008. The first type photoinitiator could be from BASF, such asIrgacure series 184, 2022, 2100, 250, 270, 295, 369, 379, 500, 651, TPO,TPO-L, 754, 784, 819, 907, 1173, or 4265. Additionally, other functionaloligomers and resin precursor composition components can be purchasedfrom Allnex Corp., such as the Ebecryl series (EB): 40, 53, 80, 81, 83,110, 114, 130, 140, 150, 152, 154, 168, 170, 180, 220, 230, 242, 246,264, 265, 270, 271, 284, 303, 350, 411, 436, 438, 450, 452, 524, 571,600, 605, 608, 657, 745, 809, 810, 811, 812, 830, 860, 870, 871, 885,888, 889, 893, 1258, 1290, 1291, 1300, 1360, 1710, 3200, 3201, 3411,3415, 3418, 3500, 3600, 3700, 3701, 3720, 4265, 4827, 4833, 4849, 4858,4883, 5129, 7100, 8100, 8296, 8301, 8311, 8402, 8405, 8411, 8412, 8413,8414, 8465, 8501, 8602, 8701, 8702, 8804, 8807, 8808, and 8810.

Example 1 Storage Modulus E′ and E′30:E′90 Ratio Control Example

The selection, formulation and/or formation of materials that have adesirable storage modulus E′ and E′30:E′90 ratio in desirable regions ofan advanced polishing pad by use of an additive manufacturing process isan important factor in assuring that the polishing results achieved bythe advanced polishing pad are uniform across a substrate. It is notedthat storage modulus E′ is an intrinsic material property of a formedmaterial, which results from the chemical bonding within a curedpolymeric material. Storage modulus may be measured at a desiredtemperature, such as 30° C. and 90° C. using a dynamic mechanicalanalysis (DMA) technique. Examples of formulations that containdifferent storage moduli are illustrated below in Table 4.

TABLE 4 Item Material Composition Formulation E′30 E′90 No. (See Table 3Ref. Name) Composition (wt %) (MPa) (MPa) E′30/E′90 1 O1:M3 45:55 4043.6 113.6 2 O1:M1 45:55 1595 169.5 9.4 3 O1:M3:M1:M2 45:22:22:11 68010.4 65.3 4 O4:O1:M3:M1:M2 30:15:22:22:11 925 385.4 2.4

Referring to Table 3 and items 1 and 2 in Table 4, creating aformulation that contains resin precursor components (e.g., monomers,oligomers, reactive diluents and other materials that contain chemicallyactive functional groups or segments) that have a higher functionalitythan other resin precursor components results in an increased storagemoduli E′ at different temperatures, while the E′30:E′90 ratio of theformed material can be decreased. Changing the resin precursor componentfrom a type M3, which has a functionality of 1, to a resin precursorcomponent of type M1, which has a functionality of 2, in the formulationincreases the storage modulus E′ at 30° C. by nearly 400%, while theE′30:E′90 ratio dropped to about 8% of its original value. Similarly,comparing items 3 and 4 in Table 4, one will note that by adding amultifunctional oligomer to a formulation that the storage moduli E′ atdifferent temperatures can be moderately increased, while the E′30:E′90ratio of the formed material can be greatly decreased. Thus, by addingthe multifunctional oligomer O4, which has a functionality of 6, to aformulation, the storage modulus E′ at 30° C. was only increased by136%, while the E′30:E′90 ratio dropped to about 4% of its originalvalue. While not intending to be bound by theory, it is believed that byincreasing the degree of crosslinking within a formed polymer material,due to the addition of components to a droplet formulation that have anincreased functionality, has a significant effect on the storage modulusE′ at higher temperatures (e.g., 90° C.) and thus has a significanteffect on the E′30:E′90 ratio. Therefore, in some embodiments of thedisclosure, precursor components that have a functionality of two orgreater are used in the formulations used to form the harder materialregions (e.g., first polishing elements 204) in the advanced polishingpad 200. In the same way, softer regions of the advanced polishing pad200 may be formed by use of formulations that have a lesserfunctionality than the harder regions in the polishing pad. Therefore,in some embodiments of the disclosure, precursor components that have afunctionality of two or less are used in the formulations used to formthe softer material regions (e.g., second polishing elements 206) in theadvanced polishing pad 200.

Example 2 Storage Modulus E′ and Percent Recovery Control Example

Examples of different formulations that can be used to adjust thestorage modulus E′ and percent recovery (%) of a material used in anadvanced polishing pad are illustrated below in Table 5.

TABLE 5 Item Material Composition Formulation Composition E′30 UTS E′30/% EL @ % No. (See Table 3 Ref. Name) (wt %) (MPa) (MPa) E′90 breakRecovery 1 O1:O2:M3:M1:M2 40:5:10:10:35 347 9.8 19 38.5 40 2O1:O2:M3:M1:M2 25:5:10:50:10 1930 19.5 11 1.9 86

Referring to items 1 and 2 in Table 5, one will note that by adjustingthe amounts of various components in a formulation that an increase instorage moduli E′ at lower temperatures (e.g., 30° C.), an increase inthe percent recovery (%) and a reduction in the percent elongation atbreak can be achieved. It is believed that the significant change in thestorage modulus E′ at 30° C., the percent recovery (%) and elongation atbreak properties are largely due to the increase in the percentage ofthe chemical components that have a high glass transition temperature(Tg). One will note that a material that has a low glass transitiontemperature, such as resin precursor component M2 (e.g., Tg=5° C.), willtend to be softer at room temperature, while a material that has a highglass transition temperature, such as resin precursor component M1(e.g., Tg=104° C.) will tend to be harder and more brittle attemperatures near room temperature. One will note in this example thatwhile the percentage of the multifunctional oligomer O1, which has afunctionality of two, is slightly decreased and percentage of the resinprecursor component M1, which also has a functionality of 2, issignificantly increased, and the change in the E′30:E′90 ratio is onlymodestly changed. Therefore, it is believed that the crosslinkingdensity is likely to be similar for polymer materials formed by thecompositions of items 1 and 2 in Table 5, which supported by the rathermodest change in the E′30:E′90 ratio of the two materials. Therefore, insome embodiments, precursor components that have a high glass transitiontemperature can be increased in a formulation to form a material thathas higher storage modulus E′, greater hardness, a greater percentage ofrecovery during processing and a smaller elongation at break. Similarly,in some embodiments, precursor components that have a low glasstransition temperature may be increased in a formulation to form amaterial that has lower storage modulus E′, lower hardness and a greaterelongation at break.

In some embodiments, it is desirable to adjust the various components ina droplet formulation used to form a low storage modulus E′ material,such that the amount of components that have a glass transitiontemperature (Tg) of less than or equal to 40° C. is greater than theamount of components that have a glass transition temperature (Tg) ofgreater than 40° C. Similarly, in some embodiments, it is desirable toadjust the various components in a droplet formulation used to form ahigh storage modulus E′ material, such that the amount of componentsthat have a glass transition temperature (Tg) of greater than 40° C. isgreater than the amount of components that have a glass transitiontemperature (Tg) of less or equal to about 40° C. In some embodiments,one or more resin precursor component materials in a droplet formulationused to form a low storage modulus E′ material in an advanced polishingpad have a glass transition temperature (Tg) of less than or equal to40° C., such as less than or equal to 30° C., and one or more resinprecursor component materials used form a droplet formulation used toform a higher storage modulus E′ material in the same advanced polishingpad have a glass transition temperature (Tg) of greater than or equal to40° C.

Example 3 Contact Angle Control Example

Examples of different formulations that can be used to adjust thecontact angle of droplets, as discussed above in conjunction with FIG.3C, that are deposited on a surface is illustrated below in Table 6. Asnoted above, it has been found that by at least controlling: 1) thecomposition of the components in a dispensed droplet during the additivemanufacturing process, 2) the amount of cure of the previously formedlayer, 3) the amount of energy from the curing device, 4) thecomposition of the surface that the dispensed droplet is disposed on,and 5) the amount of the curing agent (e.g., photoinitiator) in thedroplet composition, the contact angle α of the dispensed droplet can becontrolled to improve the control of the resolution of the featuresformed by the additive manufacturing process described herein.

TABLE 6 Item Material Composition Formulation Composition E′30 ContactAngle E′30/ Recovery No. (See Table 3 Ref. Name) (wt %) (MPa) (°) E′90(%) 1 O1:O2:M1:M2:P1 22:18:30:30:<1 2078 30 9.4 85 2O1:O2:M1:M2:O3:M4:P1:P2:A1 22.5:22.5:30:25:0.06:0.02:<1:<1:<1 1353 60 482 3 O1:O2:M1:M2:O3:M4:P1:P2:A1 27.5:17.5:30:25:0.06:0.02:<1:<1:<1 263290 4.4 79

Referring to items 1, 2 and 3 in Table 6, one will note that byadjusting the amounts of the various components in a formulation thatthe contact angle of a cured droplet or “fixed” droplet on a surfacethat was formed with same, or a similar, droplet formulation, can beadjusted. It is believed that a significant change in the contact anglecan be achieved by adjusting the type and amount of the functionalmonomers (e.g., items M1-M2 and M4) and photoinitiator components (e.g.,items P1, P2 and A1) in the dispensed droplet's formulation.

The contact angle of a droplet formulation can be improved through theuse of: 1) through or bulk cure photoinitiators (e.g., first type ofphotoinitiator) that ensure that the mechanical properties of the atleast partially cured droplets can be achieved, 2) through the use of asecond type of photo-initiator such as benzophenones and an aminesynergist, which enable a fast surface cure by reducing the ability ofO₂ in the environment to quench the free radicals generated through UVexposure (e.g., second type of photoinitiator), and 3) through surfacemodifiers that tend to make the surface of the dispensed droplet more orless polar. The surface modifiers, for example, may be used such thatwhen a drop of a hydrophilic uncured resin is deposited on a hydrophobicsurface, the surface energy of the dispensed droplet can be altered.This will result in a large contact angle, and thereby ensure that thedroplet does not “wet” the surface. The prevention of wetting of thesurface will allow the subsequently deposited droplets to be builtvertically (e.g., Z-direction). When droplet after droplet arepositioned horizontally next to each other, it is desirable to preventhorizontal wetting of the surface, so that the side walls of thevertically formed features will be formed vertically as opposed to aslopping shape. This improvement in contact angle ensures that the sidewalls of the printed features are vertical, or have gradual slopes whendeposited one on top of one another. This resolution is important in anadvanced polishing pad as the substrate contact area of the polishingfeatures needs to be maintained at a consistent contact area throughouteach polish process and/or as the pad polishing material is removed byabrasion or pad conditioning throughout the life of the pad.

Example 4 Low Storage Modulus E′ Tuning Example

The selection, formulation and/or formation of materials that have adesirable low storage modulus E′ and desirable E′30:E′90 ratio invarious regions of the advanced polishing pad can be an important factorin assuring that the static and dynamic related mechanical properties ofan advanced polishing pad can be adjusted to achieve desirable polishingresults when combined with higher storage modulus E′ material. Examplesof formulations that contain different storage moduli E′ are illustratedbelow in Table 7.

TABLE 7 Item Material Composition Formulation E′30 E′90 No. (See Table 3Ref. Name) Composition (wt %) (MPa) (MPa) E′30/E′90 1 O1:O5:M3:M5:M6:P125:25:21.4:14.3:14.3:<1 88 20 4.4 2 O1:M3:M2 45:27.5:27.5:<1 17.9 3.15.9

Referring to items 1 and 2 in Table 7, as similarly noted in Example 1above, one will note that by creating a formulation that containsmultifunctional oligomers that have a functionality of two or greaterand that have differing glass transition temperatures (Tg) the storagemoduli E′ at different temperatures can be adjusted, while the E′30:E′90ratio of the formed material can remain constant. For example, by addinga multifunctional oligomer O5, which has a functionality of 3.4 to aformulation, the storage modulus E′ at 30° C. can be increased by nearly500%, while the E′30:E′90 ratio only dropped to about 75% of itsoriginal value. While not intending to be bound by theory, it isbelieved that by increasing the degree of crosslinking within a formedpolymer material, due to the addition of multifunctional oligomer O5components to a droplet formulation, has a significant effect on thestorage modulus E′ at lower temperatures (e.g., 30° C.) when used incombination with a resin precursor component that has a relatively lowglass transition temperature Tg. Therefore, in some embodiments of thedisclosure, resin precursor components that have a functionality of twoor greater are used in combination with resin precursor components thathave a relatively low glass transition temperature Tg to form softermaterial regions (e.g., second polishing elements 206) in the advancedpolishing pad 200. Also, in some embodiments of the disclosure,precursor components and functional oligomer that have a functionalityof two or less are used in the formulations used to form the softermaterial regions (e.g., second polishing elements 206) in the advancedpolishing pad 200.

In some embodiments, it is desirable to control the properties of one ormore of the polishing elements 204, 206 in the advanced polishing pad bycontrolling the relative amounts of oligomers to monomers, or alsoreferred to herein as controlling the oligomer-monomer ratio, in a resinprecursor composition to control the amount of cross-linking within thecured material formed by the resin precursor composition. By controllingthe oligomer-monomer ratio in a resin precursor composition, theproperties (e.g., mechanical, dynamic, polishing performance, etc.) ofthe formed material can be further controlled. In some configurations,monomers have a molecular weight of less than 600. In someconfigurations, oligomers have a molecular weight of 600 or more, suchas a molecular weight of >1000. In some configurations, theoligomer-monomer ratio is defined as a weight ratio of the oligomercomponent to the monomer component, and is typically selected to achievethe desired strength and modulus. In some implementations, theoligomer-monomer ratio is from about 3:1 to about 1:19. In someimplementations the oligomer-monomer ratio is in a range from about 3:1to about 1:3 (e.g., ratio 2:1 to 1:2; ratio 1:1 to 1:3; ratio 3:1 to1:1). In one example, an oligomer-monomer ratio of 1:1 can be used toachieve desirable toughness properties such as elongation and storagemodulus E′ while maintaining printability of the formed formulation. Insome embodiments, it is desirable to select an oligomer-monomer ratiothat is greater than a 1:1 ratio, and thus contains a greater amount byweight of oligomers to monomers. A resin precursor composition that hasan oligomer-monomer ratio that is greater than a 1:1 may be used to formthe tougher or more elastomeric material regions (e.g., first polishingelements 204) in the advanced polishing pad 200. In some embodiments, itis desirable to select an oligomer-monomer ratio that is less than 1:1ratio, and thus contains a smaller amount by weight of oligomers tomonomers. A resin precursor composition that has an oligomer-monomerratio that is less than 1:1 may be used to form less elastomericmaterial regions (e.g., second polishing elements 206) in the advancedpolishing pad 200.

Example 5 Advanced Polishing Pad Properties Example

As discussed above, the additive manufacturing processes describedherein enable specific placement of material compositions with desiredproperties in specific pad areas of the advanced polishing pad, so thatthe properties of the deposited compositions can be combined to create apolishing pad that has properties that are an average of the properties,or a “composite” of the properties, of the individual materials. In oneexample, an advanced polishing pad may be formed so that it hasdesirable average tan delta (tan δ) properties over a desiredtemperature range. Curves 921-923, curves 931-933 and curve 941 in FIG.9A illustrate the average tan delta properties as a function oftemperature for differently configured and/or loaded advanced polishingpads.

FIGS. 9B and 9C are side cross-sectional views of two basicconfigurations of advanced polishing pads that were used to generate thetan delta versus temperature data, shown in FIG. 9A. The tan deltaversus temperature data found in curves 921-923 in FIG. 9A werecollected using a DMA technique that causes the advanced polishing padsamples of the type shown in FIG. 9B to be cycled in a test fixture thatloads the cantilevered samples in the Z-direction. The tan delta versustemperature data found in curves 931-933 in FIG. 9A were collected usinga DMA technique that causes the advanced polishing pad samples of thetype shown in FIG. 9B to be cycled in a test fixture that loads thecantilevered samples in the X-direction (e.g., parallel to the formedlayers). The tan delta versus temperature data found in curve 941 inFIG. 9A was collected using a DMA technique that causes the advancedpolishing pad samples of the type shown in FIG. 9C to be cycled in atest fixture that loads a cantilevered test sample in the Z-direction.During all of the tests, the advanced polishing pad samples were heatedfrom a temperature of −81° C. to a temperature of 95° C. at a ramp rateof 5° C./minute.

FIG. 9B illustrates a portion of an advanced polishing pad 200 thatcontains discrete layers of a first polishing pad material 901 and asecond polishing pad material 902 that are formed using an additivemanufacturing process described herein so that the formed layers arealigned parallel to the X-Y plane and are stacked in the Z-direction.The first polishing pad material 901 includes a low storage modulusurethane acrylate material that has a low glass transition temperature(Tg) and the second polishing pad material 902 includes a high storagemodulus urethane acrylate material that has a high glass transitiontemperature (Tg). The layers of the first polishing pad material 901 andthe second polishing pad material 902 each have a thickness 910 and 911in the Z-direction, respectively.

Referring back to FIG. 9A, the plotted data contains separate anddiscrete tan delta peaks for the first polishing pad material 901 andsecond polishing pad material 902, as shown by curves 901C and 902C. Thetan delta data for the DMA testing performed on the advanced polishingpad configuration shown in FIG. 9B are illustrated by curves 921-923 andcurves 931-933, and the tan delta data for the DMA testing performed onthe advanced polishing pad configuration shown in FIG. 9C is illustratedby curve 941.

Curves 921, 922 and 923 illustrate the effect of altering the thicknessand relative spacing of each of the layers shown in FIG. 9B when loadedin the Z-direction during testing. Curve 921 illustrates a plot of thetan delta as a function of temperature for the advanced polishing padstructure shown in FIG. 9B, which has a 50:50 composition of the firstpolishing pad material 901 to the second polishing pad material 902, andthus has equivalent thicknesses 910 and 911 in the Z-direction for eachof the layers. The thicknesses 910 and 911 in the first sample were bothabout 0.16 mm (0.006 inches). Curve 922 illustrates a plot of the tandelta as a function of temperature for the same general advancedpolishing pad structure used to generate curve 921, except that thethicknesses 910 and 911 of the layers of the first and second materials901 and 902 were both twice as large. Similarly, curve 923 illustrates aplot of the tan delta as a function of temperature for the same advancedpolishing pad structure used to generate curve 921, except thatthicknesses 910 and 911 of the layers of the first and second polishingpad materials 901 and 902 were both three times as large. One will notethat curves 921, 922 and 923 all show a blending or averaging of theproperties found in the individual materials 901 and 902, as seen by thetwo clear peaks (e.g., peaks 925 and 926) and the drop in magnitude ofeach of the peaks in the tan delta data. The two peaks found in curves921, 922 and 923 may be indicative of molecular scale mixing, chainentanglement, and/or chemical bonding formed between the first polishingpad material and the second polishing pad material. Thus, in someembodiments, molecular scale mixing, chain entanglement, and/or chemicalbonding may be desirably formed between a first material composition inthe first polishing elements and a second material composition in thesecond polishing elements with an advanced polishing pad, which can helpimprove a property of the formed advanced polishing pad (e.g., tandelta, E′30:E′90 ratio, E′30, etc.).

Curves 931, 932 and 933 illustrate the effect of altering the thicknessand relative spacing of each of the layers shown in FIG. 9B when loadedin the X-direction during testing. Curve 931 illustrates a plot of thetan delta as a function of temperature for the advanced polishing padstructure shown in FIG. 9B, which has a 50:50 composition of the firstpolishing pad material 901 to the second polishing pad material 902, andthus has equivalent widths 910 and 911 in the Z-direction for each ofthe layers. The widths 910 and 911 in the first sample were both about0.16 mm (0.006 inches). Curve 932 illustrates a plot of the tan delta asa function of temperature for the same general advanced polishing padstructure used to generate curve 931, except that the widths 910 and 911of the layers of the first and second materials 901 and 902 were bothtwice as large. Similarly, curve 933 illustrates a plot of the tan deltaas a function of temperature for the same advanced polishing padstructure used to generate curve 931, except that widths 910 and 911 ofthe layers of the first and second polishing pad materials 901 and 902were three times as large. One will note that curve 931 shows a blendingor averaging of the properties found in the individual materials 901 and902, as seen by the two clear peaks (e.g., peaks 935 and 936) and thedrop in magnitude of each of the peaks in the tan delta data. Whilecurves 932 and 933 show only a little blending or averaging of in theproperties found in the individual materials 901 and 902, as seen by thelack of the two clear peaks.

FIG. 9C illustrates a portion of an advanced polishing pad 200 thatcontains a first polishing pad feature 915 and a base layer 916 thatwere also formed using an additive manufacturing process so that thefirst polishing pad features 915 are supported by the base layer 916 andare aligned in the Z-direction (e.g., items 204 a in FIG. 2A). The baselayer 916, in this configuration, includes a 50:50 “blend” (i.e., 1:1material composition ratio) of fixed droplets of the first polishing padmaterial 901 and fixed droplets of the second polishing pad material902. The thickness of the first polishing pad features 915 and the baselayer 916 each have a width 918 and 919 that is aligned in theX-direction, respectively. Curve 941 illustrates the effect of forming acompositionally “blended” polishing pad element on the average or“composite” properties of an advanced polishing pad 200. One will notethat curve 941 shows a blending or averaging of the properties found inthe individual materials 901 and 902 found in the base layer 916, asseen by the two clear peaks (e.g., peaks 945 and 946) and the drop inmagnitude of each of the peaks in the tan delta data. The two peaksfound in curve 941 may be indicative of molecular scale mixing, chainentanglement, and/or chemical bonding formed between the first polishingpad material and the second polishing pad material within the base layer916.

The tan delta versus temperature data found in FIG. 9A illustrates thatthe structural spacing or thickness of the layers relative to theloading direction (e.g., curves 921 and 941) can have a dramatic effecton the tan delta property averaging within an advanced polishing pad.Referring to curves 931, 932 and 933 one will note that as the spacingbetween the layers of the harder and softer materials increase the morethe properties of the harder materials tend to dominate the propertiesof a formed polishing pad when loaded in a direction that is parallel tothe formed layer orientation (e.g., X-direction). However, referring tocurves 921, 922 and 923 one will note that the spacing between thelayers of the harder and softer materials has little effect on theproperties of a formed advanced polishing pad that is configured withthe polishing features aligned in an orientation that is perpendicularto the loading direction, since the measured tan delta versustemperature does not vary much as the thickness of the featuresincreases. Therefore, by controlling the structural orientation relativeto the loading direction and relative spacing of the “hard” and “soft”layers within an advanced polishing pad, one or more of the padproperties (e.g., tan delta) can be adjusted to better control thepolishing process performance of the advanced polishing pad.

Alternate Pad Structure Designs

FIG. 6 is a schematic perspective sectional view of a polishing pad 600according to one embodiment of the present disclosure. The polishing pad600 includes a second polishing element 602 that is a soft or lowstorage modulus E′ material similar to the second polishing elements 206of the 3D printed polishing pad. Similar to the second polishingelements 206, the second polishing element 602 may be formed from one ormore elastomeric polymer compositions that may include polyurethane andaliphatic segments. The polishing pad 600 includes a plurality ofsurface features 606 extending from the second polishing element 602.Outer surfaces 608 of the surface features 606 may be formed from a softor low E′ material or a composition of soft or low storage modulus E′materials. In one embodiment, the outer surface 608 of the surfacefeatures 606 may be formed from the same material or the samecomposition of materials as the second polishing element 602. Thesurface features 606 may also include a hard feature 604 embeddedtherein. The hard or high storage modulus E′ features 604 may be formedfrom a material or a composition of materials that is harder than thesurface features 606. The hard or high storage modulus E′ features 604may be formed from materials similar to the material or materials of thehard or high storage modulus E′ features 204 of the advanced polishingpad, including crosslinked polymer compositions and compositionscontaining aromatic groups. The embedded hard features 604 alter theeffective hardness of the surface features 606, and thus provide adesired target pad hardness for polishing. The soft or low storagemodulus E′ polymeric layer of the outer surface 608 can be used toreduce defects and improve planarization on the substrate beingpolished. Alternatively, a soft or low storage modulus E′ polymermaterial may be printed on surfaces of other polishing pads of thepresent disclosure to provide the same benefit.

FIG. 7 is a schematic perspective sectional view of a polishing pad 700having one or more observation windows 710. The polishing pad 700 mayhave a pad body 702. The pad body 702 may include one or more soft orlow storage modulus E′ features 706 and a plurality of first polishingelements 704 extending from the second polishing elements 706 forpolishing. The second polishing elements 706 and the first polishingelements 704 may be formed from materials similar to those for thesecond polishing element(s) 206 and first polishing elements 204 of theadvanced polishing pad 200. The first polishing elements 704 may bearranged in any suitable patterns according to the present disclosure.

The one or more observation windows 710 may be formed from a transparentmaterial or compositions to allow observation of the substrate beingpolished. The observation windows 710 may be formed through, and/orabout portions of, the second polishing elements 706 or the firstpolishing elements 704. In some embodiments, the observation window 710may be formed from a material that is substantially transparent, andthus is able to transmit light emitted from a laser and/or white lightsource for use in a CMP optical endpoint detection system. The opticalclarity should be high enough to provide at least about 25% (e.g., atleast about 50%, at least about 80%, at least about 90%, at least about95%) light transmission over the wavelength range of the light beam usedby the end point detection system's optical detector. Typical opticalend point detection wavelength ranges include the visible spectrum(e.g., from about 400 nm to about 800 nm), the ultraviolet (UV) spectrum(e.g., from about 300 nm to about 400 nm), and/or the infrared spectrum(e.g., from about 800 nm to about 1550 nm). In one embodiment,observation window 710 is formed from a material that has atransmittance of >35% at wavelengths between 280-800 nm. In oneembodiment, observation window 710 is formed from a material that has atransmittance of >35% at wavelengths between 280-399 nm, and atransmittance of >70% at wavelengths between 400-800 nm. In someembodiments, the observation window 710 is formed from a material thathas a low refractive index that is about the same as that of thepolishing slurry and has a high optical clarity to reduce reflectionsfrom the air/window/water interface and improve transmission of thelight through the observation window 710 to and from the substrate.

In one embodiment, the observation window 710 may be formed from atransparent printed material, including polymethylmethacrylate (PMMA).In another embodiment, the window is formed using transparent polymericcompositions that contain epoxide groups, wherein the compositions maybe cured using a cationic cure, and may provide additional clarity andless shrinkage. In a similar embodiment, the window may be formed from amixture of compositions that undergo both cationic and free radicalcure. In another embodiment, the window may be produced by anotherprocess, and may be mechanically inserted into a preformed opening inthe polishing pad that is formed by a 3D process.

FIG. 8 is a schematic perspective sectional view of a polishing pad 800including a backing layer 806. The polishing pad 800 includes a secondpolishing element 804 and a plurality of first polishing elements 802protruding from the second polishing element 804. The polishing pad 800may be similar to any of the polishing pads 200, 600, 700 describedabove, with the exception that the backing layer 806 attached to thesecond polishing element 804. The backing layer 806 may provide adesired compressibility to the polishing pad 800. The backing layer 806may also be used to alter the overall mechanical properties of thepolishing pad 800 to achieve a desired hardness and/or have desiredstorage modulus E′ and loss modulus E″. The backing layer 806 may have ahardness value of less than 80 Shore A scale. In one embodiment, thebacking layer 806 may be formed from an open-cell or a closed-cell foam,such as polyurethane or polysiloxane (silicone), so that under pressurethe cells collapse and the backing layer 806 compresses. In anotherembodiment, the backing layer 806 may be formed from natural rubber,EPDM rubber (ethylene propylene diene monomer), nitrile, or neoprene(polychloroprene).

In one embodiment, the materials of the first polishing element 204 andsecond polishing element 206 are chemically resistant to attack from thepolishing slurry. In another embodiment, the materials of firstpolishing element 204 and second polishing element 206 are hydrophilic.The hydrophilic and hydrophobic nature of the polishing pad may beadjusted by judicious choice of formulation chemistries by those skilledin the art.

Although polishing pads described herein are circular in shape,polishing particles according to the present disclosure may include anysuitable shape, such as polishing webs configured to move linearlyduring polishing.

Compared with traditional polishing pads, the advanced polishing paddisclosed herein has several manufacturing and cost related advantages.For example, traditional polishing pads generally include a machined andtextured polishing surface that is supported by a subpad formed from asoft or low storage modulus E′ material, such as a foam, to obtaintarget hardness and/or a storage modulus E′ for polishing substrates.However, by selecting materials having various mechanical properties andadjusting the dimensions and arrangement of the different featuresformed on an advanced polishing pad the same properties can be achievedin the pad body of the advanced polishing pad without the need for asubpad. Therefore, the advanced polishing pad reduces a user's cost ofownership by eliminating the need for a subpad.

The increased complexity of polishing pad designs that will be requiredto polish the next generation IC devices greatly increases themanufacturing complexity of these polishing pads. There are non-additivemanufacturing type processes and/or subtractive process which may beemployed to manufacture some aspects of these complex pad designs. Theseprocesses may include multi-material injection molding and/or sequentialstep UV casting to form material layers from single discrete materials.These forming steps are then typically followed by machining and postprocessing using milling, grinding or laser ablation operations or othersubtractive techniques.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A method of forming a polishing article, comprising sequentiallyforming a plurality of acrylate polymer layers, wherein forming theplurality of acrylate polymer layers comprises: mixing a first amount ofa first resin precursor component, a second amount of a second resinprecursor component, and a first amount of a first curing agent to forma first precursor formulation that has a first viscosity that enablesthe first precursor formulation to be dispensed using an additivemanufacturing process; mixing a third amount of a third resin precursorcomponent, a fourth amount of a fourth resin precursor component and asecond amount of a second curing agent to form a second precursorformulation that has a second viscosity that enables the secondprecursor formulation to be dispensed using an additive manufacturingprocess; dispensing a first amount of the first precursor formulation ona first region of a surface by use of the additive manufacturingprocess; dispensing a first amount of the second precursor formulationon a second region of the surface by use of the additive manufacturingprocess; and exposing the dispensed first amount of the first precursorformulation and the dispensed first amount of the second precursorformulation to electromagnetic radiation for a first period of time toonly partially cure the first amount of the first precursor formulationand the first amount of the second precursor formulation.
 2. The methodof claim 1, wherein the first resin precursor component and the thirdresin precursor component each comprise a multifunctional urethaneoligomer, a polyester acrylate oligomer, a polyether acrylate oligomer,or an epoxy acrylate oligomer.
 3. The method of claim 2, wherein thesecond resin precursor component or the fourth resin precursor componentare selected from a group consisting of a monofunctional acrylatemonomer or a multifunctional acrylate monomer.
 4. The method of claim 3,wherein the first and the second curing agents each comprise aphotoinitiator selected from a group consisting of benzoin ethers,benzyl ketals, acetyl phenones, alkyl phenones, phosphine oxides,benzophenone compounds, and thioxanthone compounds.
 5. The method ofclaim 3, wherein the ratio of the first resin precursor component to thesecond resin precursor component in the first precursor formulation byweight is from about 3:1 to about 1:3.
 6. The method of claim 1, whereinthe first period of time is less than or equal to 1 second.
 7. Themethod of claim 1, wherein the partially cured droplets of the firstprecursor formulation and the partially cured droplets of the secondprecursor formulation have a contact angle relative to the surface ofgreater than or equal to 50 degrees.
 8. The method of claim 7, whereinthe surface comprises a material formed by partially curing an amount ofthe first precursor formulation or an amount of the second precursorformulation.
 9. The method of claim 1, wherein the first resin precursorcomponent comprises a material that has a glass transition temperaturethat is greater than 40° C., and the first amount of the first resinprecursor component is greater than the second amount of the secondresin precursor component in the first precursor formulation, and thethird resin precursor component comprises a material that has a glasstransition temperature that is less than 40° C., and the third amount ofthe third resin precursor component is greater than the fourth amount ofthe fourth resin precursor component in the second precursorformulation.
 10. The method of claim 1, wherein the first resinprecursor component and the third resin precursor component eachcomprise a multifunctional urethane acrylate oligomer; the second resinprecursor component is a multifunctional acrylate monomer; the firstcuring agent comprises an amine synergist and a photoinitiator selectedfrom a group consisting of benzophenone compounds and a thioxanthonecompounds, and the second curing agent comprises a photoinitiatorselected from a group consisting of benzoin ethers, benzyl ketals,acetyl phenones, alkyl phenones, and phosphine oxides.
 11. The method ofclaim 1, wherein exposing the dispensed first amount of the firstprecursor formulation and the dispensed first amount of the secondprecursor formulation to electromagnetic radiation is performed in anenvironment that has an oxygen concentration that is less than air. 12.The method of claim 1, further comprising: dispensing a first amount ofa third precursor formulation to form at least a portion of thepolishing article; and exposing the dispensed first amount of the thirdprecursor formulation to electromagnetic radiation to at least partiallycure the dispensed first amount of the third precursor formulation,wherein the formed portion has a transmittance of >35% at wavelengthsbetween 280-399 nm, and a transmittance of >70% at wavelengths between400-800 nm in the formed polishing article.
 13. The method of claim 12,wherein the third precursor formulation comprises a material selectedfrom a group consisting of polymethylmethacrylate (PMMA) and an epoxidegroup containing material.
 14. A resin precursor composition for formingat least a portion of a polishing article, comprising: a first precursorformulation comprising: a first resin precursor component that comprisesa multifunctional acrylate oligomer; a second resin precursor componentthat comprises multifunctional acrylate monomer; and a first curingagent that comprises a photoinitiator selected from a group consistingof benzoin ethers, benzyl ketals, acetyl phenones, alkyl phenones,phosphine oxides, benzophenone compounds, and thioxanthone compounds,wherein the first precursor formulation has a first viscosity thatenables the first precursor formulation to be dispensed to form aportion of the polishing article by use of an additive manufacturingprocess.
 15. The resin precursor composition of claim 14, wherein thefirst resin precursor component comprises an aliphatic multifunctionalurethane acrylate that has a functionality that is greater than or equalto
 2. 16. The resin precursor composition of claim 15, wherein thesecond resin precursor component comprises a material selected from agroup consisting of 2-ethylhexyl acrylate, octyldecyl acrylate, cyclictrimethylolpropane formal acrylate, caprolactone acrylate andalkoxylated lauryl methacrylate.
 17. The resin precursor composition ofclaim 14, wherein the ratio of the first resin precursor component tothe second resin precursor component by weight is from about 3:1 toabout 1:3.
 18. The resin precursor composition of claim 17, wherein thefirst viscosity is from about 15 cP to about 30 cP at 70° C.
 19. Theresin precursor composition of claim 14, wherein the first resinprecursor component comprise an aliphatic multifunctional urethaneacrylate oligomer, and the second resin precursor component is selectedfrom a group consisting of a monofunctional acrylate monomer or amultifunctional acrylate monomer.
 20. The resin precursor composition ofclaim 14, wherein the first resin precursor component comprises amaterial that has a glass transition temperature that is greater than40° C., and an amount of the first resin precursor component is greaterthan an amount of the second resin precursor component in the firstprecursor formulation.
 21. A method of forming a polishing article,comprising forming a plurality of urethane acrylate polymer layers,wherein forming the plurality of urethane acrylate polymer layerscomprises: dispensing a plurality of droplets of a first precursorformulation in a first pattern across a surface of a polishing body thatcomprises a first material composition, wherein the first precursorformulation comprises a first multifunctional urethane acrylateoligomer, a first resin precursor component and a first amount of afirst curing agent; dispensing a plurality of droplets of a secondprecursor formulation in a second pattern across the surface of thepolishing body, wherein the second precursor formulation comprises thefirst multifunctional urethane acrylate oligomer and a second resinprecursor component; and exposing the dispensed droplets of the firstprecursor formulation and the dispensed droplets of the second precursorformulation to electromagnetic radiation for a first period of time toonly partially cure the droplets of the first precursor formulation andthe droplets of the second precursor formulation.
 22. The method ofclaim 21, wherein the first pattern of droplets of the first precursorformulation are used to form a first feature of the polishing articleand the second pattern of droplets of the second precursor formulationare used to form a second feature of the polishing article, and theformed first feature comprises a polishing surface.
 23. The method ofclaim 21, wherein the first and the second precursor formulations eachfurther comprise a photoinitiator selected from a group consisting ofbenzoin ethers, benzyl ketals, acetyl phenones, alkyl phenones,phosphine oxides, benzophenone compounds, or thioxanthone compounds. 24.The method of claim 21, wherein the first resin precursor componentcomprises a material that has a glass transition temperature that isgreater than 40° C., and the second resin precursor component comprisesa material that has a glass transition temperature that is less than 40°C.
 25. The method of claim 21, wherein exposing the dispensed dropletsof the first precursor formulation and the second precursor formulationto electromagnetic radiation is performed in an environment that has anoxygen concentration that is less than air.
 26. The method of claim 21,further comprising: dispensing a plurality of droplets of a thirdprecursor formulation to form at least a portion of the polishingarticle; and exposing the dispensed droplets of the third precursorformulation to electromagnetic radiation to at least partially cure theplurality of droplets of the third precursor formulation, wherein theformed portion has a transmittance of >35% at wavelengths between280-399 nm and a transmittance of >70% at wavelengths between 400-800 nmin the formed polishing article.